How to buy or build an ADU in Los Angeles County to help pay the mortgage: state ADU law, LADBS and county permits, the rent math, how lenders count ADU income, and property taxes at 7.40%

In Los Angeles County, a backyard can be worth more than a lawn. California's accessory dwelling unit (ADU) law lets most owners of a single-family home add a rentable unit, and the three big mortgage players, Fannie Mae, Freddie Mac, and FHA, now let buyers count part of the ADU's rent as income when they qualify. With the county's median listing price at $950,000 and Freddie Mac's 30-year average (Primary Mortgage Market Survey, PMMS) at 7.40% for the week of October 15, a buyer putting 20% down on the median faces about $5,262 a month in principal and interest. HUD's revised fiscal year 2026 fair market rent for a one-bedroom unit in the Los Angeles area is $2,328, a benchmark, not a promise of what a unit will rent for. That is the case for an ADU in one sentence: one rented unit at that benchmark would equal about 44% of the median home's principal and interest. This guide explains what the latest numbers say, what state law lets you build, how permitting works in the City of Los Angeles and in unincorporated county areas, how to run the cost and rent math yourself, how lenders count ADU rent, what happens to your property tax, and the mistakes to avoid when you buy a home that already has a unit out back.

The market behind the numbers

Realtor.com's September 2026 data put Los Angeles County's median listing price at $950,000, down from $965,000 in August and 4.5% below the $995,000 median of September 2025. That matches January 2026 as the county's lowest median listing price since February 2023. The median listing price per square foot was $620, down from $638 a year earlier, and the median listed home was 1,673 square feet, down from 1,717. These figures cover houses and condos together.

There were 15,374 active listings in September, about 4.1% more than the 14,764 of a year earlier. New listings fell to 5,670 from 5,882 (down about 3.6%), and pending listings, homes with an accepted offer that had not yet closed, fell to 4,984 from 5,450, a drop of about 8.6%. Realtor.com's pending ratio, pendings divided by actives, slipped to about 0.32 from about 0.37. The median listing spent 56 days on the market, up from 54 in August but below the 57 days of September 2025.

The price-cut share. Realtor.com reports that about 15.9% of Los Angeles County listings had a price reduction in September, up from 15.6% in August and 14.7% in September 2025; only 0.9% raised their price. Los Angeles had the lowest share of the five Southern California counties Choice of America serves: Orange County was at 21.1%, San Diego County 20.4%, San Bernardino County 18.1%, and Riverside County 17.0%.

The rate. Freddie Mac's average 30-year fixed rate was 7.40% in the weeks of October 8 and October 15, 2026, up from 6.27% a year earlier. The 15-year fixed averaged 6.71% on October 15. The next weekly reading is due Thursday, October 22.

What that means for a buyer. As an illustration, 20% down on the $950,000 median means a $760,000 loan. At 7.40%, principal and interest is about $5,262 a month. On last September's $995,000 median at 6.27%, the same 20%-down loan of $796,000 would have cost about $4,911. The median listing price fell $45,000, yet the payment is still about $351 a month higher. You can check it with a spreadsheet: =PMT(0.074/12, 360, -760000) returns about $5,262. These figures exclude property taxes, insurance, HOA dues, and mortgage insurance.

What an ADU could offset. HUD's revised fiscal year 2026 fair market rents for the Los Angeles-Long Beach-Glendale area, effective May 21, 2026, are $2,079 for a studio, $2,328 for one bedroom, and $2,903 for two bedrooms. HUD sets these at the estimated 40th percentile of rents, and they are gross rents that include utilities, so they are a benchmark, not a promise of what your unit will rent for. At those benchmarks, a rented studio would equal about 40% of the median home's $5,262 principal and interest, a one-bedroom about 44%, and a two-bedroom about 55%.

ADUs are not a niche. California's Department of Housing and Community Development (HCD) reports that the number of ADUs permitted statewide each year grew from 1,336 in 2016 to 30,354 in 2024, and that ADUs made up more than 26.6% of all homes permitted in California in 2024.

Step 1: Learn what state law lets you build

California's ADU rules now live in Government Code sections 66310 through 66342 (they were renumbered in 2024 by SB 477). Cities and the county can set some local standards, but state law sets the floor. The key rules:

• Where: an ADU is allowed on a lot zoned for single-family or multifamily residential use with an existing or proposed home. It can be attached, built inside the home (including an attached garage), converted from a detached garage or other accessory structure, or detached (Gov. Code section 66314).
• Approval is ministerial. A permit application must be approved or denied without discretionary review or a public hearing. The agency must tell you within 15 business days whether your application is complete, and must approve or deny a complete application within 60 days when there is already a home on the lot; if it does not act in time, the application is deemed approved. A denial must come with a written list of what is deficient and how to fix it (section 66317).
• Size: a detached ADU can be up to 1,200 square feet; an attached ADU generally cannot exceed 50% of the existing home's floor area. A local agency cannot set a maximum below 850 square feet, or 1,000 square feet for a unit with more than one bedroom, and cannot use lot coverage, floor-area ratio, open space, or front-setback rules to block an ADU of at least 800 square feet with four-foot side and rear setbacks (sections 66314 and 66321).
• Height: local rules must allow at least 16 feet for a detached ADU, 18 feet within a half-mile walk of a major transit stop or high-quality transit corridor (plus two feet to match the main home's roof pitch), and up to 25 feet, or the main home's height limit if lower, for an attached ADU (section 66321).
• Setbacks: no more than four feet from side and rear lot lines for a new structure, and none for a conversion of existing space or a rebuild in the same footprint (section 66314(d)(7)).
• Parking: no more than one space per unit or per bedroom, whichever is less, and none can be required for an ADU within a half-mile walk of public transit, in an architecturally and historically significant historic district, built within the existing home or an accessory structure, where on-street parking permits are required but not offered to the ADU occupant, or within one block of a car-share vehicle (sections 66314 and 66322, as summarized by HCD). If you tear down or convert a garage to build the ADU, the city cannot make you replace that parking.
• Fire sprinklers: not required in the ADU if they are not required for the main home, and building an ADU cannot trigger sprinklers in the main home (section 66314).
• Owner-occupancy: cities and counties cannot require you to live on the property to have an ADU (section 66315). Junior ADUs are the exception; they require owner-occupancy (section 66333).
• Combinations: on a single-family lot, you can generally do one ADU plus one junior ADU (a unit of up to 500 square feet inside the home). Lots with existing apartment buildings can add units in non-livable space and up to eight detached ADUs, not exceeding the number of existing units (section 66323).
• Rentals: you may rent the ADU, and agencies may require rental terms of 30 days or longer (section 66315); ADUs created under section 66323 and junior ADUs must be rented for terms longer than 30 days. In other words, plan on a long-term tenant, not a short-term rental.
• Selling separately: an ADU generally cannot be sold separately from the main home. The exceptions are a narrow nonprofit-buyer program (section 66341) and a local ordinance allowing condominium conversion (section 66342), which only applies if your city has adopted one.

How to do it:

1. Find your zoning. In the City of Los Angeles, look up your parcel on the city's ZIMAS system; in unincorporated areas, use LA County Planning's zoning tools. Each other city in the county has its own planning department.
2. Check for overlays that change the details: hillside areas, very high fire hazard severity zones, coastal zones, historic districts, flood zones, and methane zones.
3. Decide on the type: a garage conversion or interior unit is often the least expensive path, a detached new unit gives the most privacy, and a junior ADU can be the smallest step if you have a spare bedroom with an outside door.

Step 2: Know who issues the permit, and use pre-approved plans

Los Angeles County is not one permitting system. The City of Los Angeles, unincorporated county areas, and each other city all review their own ADUs, within the state rules above.

City of Los Angeles (LADBS). The city adopted its ADU ordinance (Ordinance 186,481) on December 11, 2019, effective December 19, 2019, adding Los Angeles Municipal Code section 12.22 A.33 with local standards for ADUs, junior ADUs, and movable tiny houses. The Department of Building and Safety runs an ADU Standard Plan Program: plans designed by private architects and engineers are pre-approved for the building, residential, and green codes, so plan check for your project focuses on your site, zoning, and foundation. The city also owns a pre-approved one-story, one-bedroom design, YOU-ADU (about 455 square feet on LADBS's listing), that owners can use free of charge. Many earlier private standard plans on the city's list are marked expired, so confirm a plan's status before you buy it.

Unincorporated Los Angeles County. For unincorporated areas, LA County Planning and Public Works Building and Safety offer three free pre-approved plans: Plan A (1,200 square feet, 3 bedrooms, 1 bath), Plan B (1,200 square feet, 2 bedrooms, 1 bath), and Plan C (800 square feet, 1 bedroom, 1 bath). You add a site plan, file a Regional Planning base application through EPIC-LA, get the site-specific plot plan approved, then submit the building permit package with Title 24 energy calculations. The county plans cannot be modified (they can be mirrored or rotated), and the plan sheets say they do not apply to hillside properties, very high fire hazard severity zones, geologic, methane, or flood hazard zones, restricted-use areas, septic-tank areas, or properties with enforcement cases. Once a permit is issued, you must request your first inspection within 12 months and a follow-up inspection at least every 180 days to keep it from expiring. For fire rebuilds, the county also publishes a separate pre-approved catalog, including ADU designs for the Foothills area that meet high fire hazard severity zone (Chapter 7A) construction requirements.

How to do it:

1. Book a pre-application consultation with your city or the county (LA County offers virtual counseling) and bring your parcel number, a rough site sketch, and photos.
2. Choose a design path: a free city or county plan, a purchased pre-approved private plan, or a custom design by a licensed architect or designer.
3. Order a survey and check utilities early: where sewer and water lines run, whether your electrical panel can handle the new load, and whether a utility will require a new or separate connection. Conversions of existing space under section 66323 cannot be required to get a new connection; other ADUs may be (HCD ADU Handbook, Gov. Code section 66311.5).
4. Track the clock. If the agency misses the 15-business-day completeness deadline, or, with an existing home on the lot, the 60-day decision deadline, state law treats the application as complete or deemed approved; ask for written determinations.
5. Hire licensed professionals and verify contractor licenses with the Contractors State License Board.

Step 3: Budget the full cost, including the fees state law limits

Construction costs vary widely with size, site, design, and finishes, so the only reliable number is a written bid on your lot. What state law does control are fees:

• Impact fees: state law exempts an ADU of 750 square feet or less of interior living space from impact fees charged by local agencies, special districts, and water companies (Gov. Code section 66311.5); permit and plan-check fees still apply. Above 750 square feet, impact fees must be proportional to the ADU's size compared with the main home. HCD's example: a 1,000-square-foot ADU on a lot with a 2,000-square-foot home could be charged 50% of the fee for a new home.
• School fees: school districts may charge fees on ADUs larger than 500 square feet; ADUs under 500 square feet are not subject to school impact fees (Education Code section 17620).
• Utility connection fees: ADUs converted from existing space and junior ADUs are not treated as a new residential use for connection fees unless built at the same time as a new home; otherwise connection fees must be proportional to the ADU's burden (HCD ADU Handbook, citing Gov. Code section 66311.5).
• Grants: CalHFA's ADU Grant Program reimbursed up to $40,000 of predevelopment costs, but HCD's March 2026 handbook says those funds are exhausted. Ask your city about local fee waivers or programs.

How to do it:

1. Get at least three written bids on the same plan, each broken into design, permits and fees, site work, utilities, structure, finishes, and contingency.
2. Design to the thresholds: at 750 square feet or less, you avoid impact fees; under 500, you also avoid school fees. Permit fees still apply.
3. Add a contingency for surprises in older LA homes: sewer laterals, electrical service upgrades, and soils.
4. Price your financing: a cash-out refinance, home equity line, renovation loan (Fannie Mae HomeStyle Renovation or Freddie Mac CHOICERenovation), or construction-to-permanent loan. Get written quotes; rates on these products differ from the 30-year purchase rate.

Step 4: Run the rent and cash-flow math yourself

Here is the method, using HUD's one-bedroom benchmark of $2,328 and the 7.40% 30-year rate. All construction costs and operating assumptions below are hypothetical, chosen to show the method; replace them with your own bids and local rent comparables.

Hypothetical operating assumptions: rent of $2,328 a month; 5% vacancy ($116); 8% for maintenance and reserves ($186); $100 a month added insurance; $150 a month in utilities paid by you (FMRs include utilities); and new property tax of 1% of the construction cost (see Step 6).

Three lessons come out of that table. First, cost control matters more than anything else: a garage conversion or modest one-bedroom can pay for itself from rent even at 7.40%, while an expensive build financed entirely at today's rates may not. Second, if you pay cash or use low-cost existing equity, the ADU's return is the yield column, which you can compare with what that money earns elsewhere. Third, an ADU can still make sense with thin cash flow if it houses a family member, adds long-term value, or gives you flexibility to move into it later and rent the main house.

How to do it:

1. Find real rent comparables: rented ADUs, guest houses, and small units within a mile, same bedroom count, similar size and parking. Use HUD's FMR only as a cross-check.
2. Write a monthly pro forma with every line in the table above, using your own bids, insurance quote, and tax rate.
3. Run it three ways: your expected rent, 10% lower, and with two months vacant.
4. Check the payback: divide total cost by annual net rent to see how many years it takes to recover your outlay.

Step 5: If you are buying, learn how lenders count ADU rent

This is where an ADU changes what you can buy. Each agency has its own rules, and all three use similar guardrails:

• Fannie Mae. In October 2025 (Selling Guide Announcement SEL-2025-08), Fannie Mae began allowing rental income from an ADU on a one-unit principal residence, for purchase and limited cash-out refinance loans. Rent can come from only one existing ADU, and the ADU income used to qualify is capped at 30% of total qualifying income. For a purchase, the lender starts from 75% of the monthly gross rent, supported by the appraiser's comparable rent schedule (Form 1007) and a lease if one transfers with the sale (Selling Guide B3-3.8-02). Fannie Mae said its Desktop Underwriter would apply the ADU rules starting with version 12.1 in the first quarter of 2026, and lenders could apply them right away on manually underwritten loans. Fannie Mae allows only one ADU per one-unit property and does not allow ADUs with two- to four-unit homes (B2-3-04).
• Freddie Mac. ADU rent on a one-unit primary residence can be used for a purchase or "no cash-out" refinance; rent documented with a lease counts at no more than 75% of the lease amount, and qualifying ADU rent cannot exceed 30% of total qualifying income. The appraisal must include at least one comparable sale with an ADU and at least three comparable rentals, at least one of them a rented ADU (Freddie Mac ADU fact sheet, February 2026).
• FHA. Under Mortgagee Letter 2023-17, the lender uses 75% of the lesser of the appraiser's fair market rent or the lease rent, the ADU income cannot exceed 30% of total monthly effective income, and the borrower must have two months of mortgage payments (PITI) in reserves after closing when ADU rent is used. HCD notes that FHA's 203(k) rehabilitation loan can be used to build an attached ADU only.
• Loan size. The 2026 conforming and FHA one-unit loan limit in Los Angeles County is $1,249,125 (FHFA); a home with an ADU is still a one-unit property for this purpose.

Worked example (hypothetical). A buyer earns $12,000 a month in wages and buys a home with a permitted one-bedroom ADU that the appraiser supports at $2,328 a month. Lenders generally use 75% of the rent, or $1,746 a month. Total qualifying income becomes $13,746, of which the ADU is about 12.7%, well under the 30% cap. If the lender's maximum total debt-to-income ratio were 45% (a hypothetical figure; limits vary by loan and lender), that extra income would support about $786 more in monthly payments, or roughly $113,000 more loan at 7.40% over 30 years. The 30% cap matters for lower-income buyers: to use the full $1,746, total qualifying income must be at least $5,820 a month ($1,746 divided by 30%).

How to do it:

1. Ask your loan officer, in writing, which program they will use, whether they will count ADU rent, and how they calculate it.
2. Make sure the ADU is permitted (Step 7); lenders and appraisers look at whether it is legal.
3. Ask for an appraiser with ADU experience and for the comparable rent schedule (Form 1007).
4. Get the current lease and rent history from the seller if a tenant is staying.
5. Plan the reserves: FHA requires two months of PITI (principal, interest, taxes, and insurance) in reserve when ADU rent is used (Mortgagee Letter 2023-17).

Step 6: Understand the property tax, and why your house is not reassessed

Under Proposition 13, adding new construction does not reassess your whole property. The Los Angeles County Assessor lists adding an ADU or junior ADU, attached or detached, as assessable new construction, and explains that the value of the new construction is added to your existing assessed value, which then grows only by the annual inflation adjustment of up to 2%. Your existing home keeps its original base year value. The Assessor adds its own appraised value for the new ADU, which may differ from what you spent to build it.

Worked example (hypothetical). A longtime owner's home is assessed at $600,000. If the Assessor values a new ADU at $250,000, the assessed value rises to $850,000, adding about $2,500 a year at the 1% base tax rate, plus your area's voter-approved rates. A buyer paying the $950,000 median for a home would start at about $9,500 a year at the 1% base rate, before voter-approved rates. A 2024 bill that would have temporarily excluded new ADUs from assessment (SB 1164) did not become law.

How to do it:

1. Look up your tax rate on your current bill (the 1% base plus voter-approved rates and direct assessments).
2. Expect supplemental tax bills after completion. The Assessor explains that completed new construction triggers a supplemental assessment, that completion between January 1 and May 31 produces two supplemental bills, and that supplemental bills go directly to you and generally are not paid through your impound account, so budget for them.
3. Keep your final costs and permit records; you can appeal the new construction value if you believe it is too high.

Step 7: If you are buying a home that already has a unit, verify it is legal

Many Los Angeles homes have a "guest house" or converted garage that was never permitted. That matters for financing, insurance, rental income, and safety.

How to do it:

1. Pull the permit history from LADBS's online building records (City of Los Angeles) or from your city or the county, and compare it with the listing and the appraisal.
2. Check the certificate of occupancy or final inspection for the unit, and confirm the bedroom count matches.
3. Ask the seller in writing about permits, tenants, leases, deposits, and rent history, and review the disclosures.
4. If it is unpermitted, price the fix: state law bars agencies from denying a permit for an unpermitted ADU built before January 1, 2018, only because it violates building standards or ADU rules, unless correcting the violation is necessary for health and safety or the building is substandard (HCD ADU Handbook, Gov. Code section 66311.7). Homeowners may get a confidential third-party code inspection from a licensed contractor before applying.
5. Know the tenant rules: if a tenant is staying, the lease transfers with the sale. California's statewide rent cap (Civil Code section 1947.12) exempts housing issued a certificate of occupancy within the previous 15 years, but other state and local tenant protections may apply, and some cities, including Los Angeles, have their own rules. Ask a landlord-tenant attorney before you rely on vacating a unit.

Step 8: Become a landlord the right way

How to do it:

1. Screen tenants consistently under fair housing rules, use a written lease, and collect a deposit within legal limits.
2. Update your insurance to cover the ADU and a rental (a landlord policy or endorsement), and consider umbrella liability coverage.
3. Keep records for taxes: rental income is taxable, and expenses and depreciation on the ADU may offset it; talk with a tax professional before you start.
4. Plan for long-term rentals, since state law allows agencies to require rental terms of 30 days or longer (section 66315).
5. Revisit your numbers every year: rent, insurance, taxes, and repairs.

Step 9: Put it together: buy, build, or both

A sample path for a buyer:

• Before you shop: get preapproved and ask whether the lender will count ADU rent; set rent and price targets.
• While shopping: filter for properties with permitted ADUs, guest houses, or lots and garages that suit a future ADU; check zoning and overlays.
• In escrow: verify permits, leases, and rent; get the appraisal with Form 1007; get insurance quotes for both units.

A sample path for an owner adding an ADU:

• Month 1: zoning check, survey, utility review, and a pre-application meeting.
• Months 1 to 3: choose a pre-approved or custom plan; collect bids; line up financing.
• Permit stage: submit; track the 15-business-day completeness and 60-day decision deadlines.
• Construction: schedule inspections on time (the county requires the first within 12 months and follow-ups every 180 days).
• After completion: final inspection, insurance update, lease-up, and the supplemental tax bill. Plan on long-term tenants: cities may require rental terms of 30 days or longer (section 66315), and ADUs created under section 66323 and junior ADUs must be rented for terms longer than 30 days.

An ADU checklist for Los Angeles County

1. Zoning and overlays checked (hillside, fire zone, coastal, historic, flood, methane)
2. Permitting agency identified: LADBS, LA County, or your city
3. Pre-approved plan options reviewed (city YOU-ADU; county Plans A, B, C for unincorporated areas; fire-rebuild catalog)
4. Three written bids; size compared with the 750- and 500-square-foot fee thresholds
5. Financing quotes in writing (cash-out, HELOC, renovation, or construction loan)
6. Pro forma with rent comps, vacancy, maintenance, insurance, utilities, and new property tax
7. For buyers: lender confirms ADU rent counting (75% of rent, 30% cap) and reserves
8. For buyers: permits, certificate of occupancy, leases, and rent history verified
9. Insurance updated; tax professional consulted on rental income
10. Tenant protections reviewed with an attorney if a tenant is in place

What this means day to day

From Long Beach, Torrance, and Inglewood to Pasadena, Glendale, Burbank, the San Fernando Valley, Santa Clarita, and the Antelope Valley, Los Angeles County households are looking for ways to make a 7.40% mortgage work. With the median listing price down 4.5% from a year ago but payments still higher, an ADU can turn part of a lot into income, house a parent or adult child, or help a buyer qualify. The owners who do best treat it like a small real estate project: confirm the rules, control the cost, run the rent math honestly, and verify every permit.

At Choice of America, we help Los Angeles County buyers find homes with permitted ADUs or ADU-ready lots, compare lender approaches to ADU income, and run the numbers before you write an offer, and we help owners think through whether adding a unit makes sense before selling or refinancing. Visit our Los Angeles County page for local guidance, or call or text us to run the numbers on your home.

Choice of America · Los Angeles County real estate

Dr. Hamid Rowshan, DRE #02004794, company DRE #02240008. Choice of America, serving Orange, Los Angeles, Riverside, San Bernardino, and San Diego counties. Call or text 833-THIS-BROKER, (833) 842-7465.

Payment figures are illustrations based on the September 2026 median listing price, a 20% down payment, and Freddie Mac's 30-year PMMS average for the week of October 15, principal and interest only; they are not a loan quote. HUD fair market rents are 40th-percentile gross rent benchmarks, not appraisals of any unit. The $150,000, $250,000, and $350,000 construction costs, the vacancy, maintenance, insurance, and utility amounts, the $12,000 monthly wages, the 45% debt-to-income limit, and the $600,000 assessed value are hypothetical, used only to show the method. ADU law, local ordinances, lender guidelines, and tax rules are summarized and can change; confirm with your city or county, lender, contractor, attorney, and tax professional. This article is general information, not legal, tax, or lending advice.

Sources:

• Realtor.com Residential Data, county inventory core metrics (September 2026 and history; median listing price, price per square foot, median square feet, active, new and pending listings, days on market, price_reduced_share, price_increased_share, pending ratio, five-county comparison): https://www.realtor.com/research/data/ (county files: https://econdata.s3-us-west-2.amazonaws.com/Reports/Core/RDC_Inventory_Core_Metrics_County.csv and https://econdata.s3-us-west-2.amazonaws.com/Reports/Core/RDC_Inventory_Core_Metrics_County_History.csv)
• Realtor.com via FRED (same data series), Los Angeles County, CA: Median Listing Price (MEDLISPRI6037) https://fred.stlouisfed.org/series/MEDLISPRI6037; Median Listing Price per Square Feet (MEDLISPRIPERSQUFEE6037) https://fred.stlouisfed.org/series/MEDLISPRIPERSQUFEE6037; Median Days on Market (MEDDAYONMAR6037) https://fred.stlouisfed.org/series/MEDDAYONMAR6037; Active Listing Count (ACTLISCOU6037) https://fred.stlouisfed.org/series/ACTLISCOU6037; Pending Listing Count (PENLISCOU6037) https://fred.stlouisfed.org/series/PENLISCOU6037; New Listing Count (NEWLISCOU6037) https://fred.stlouisfed.org/series/NEWLISCOU6037
• Freddie Mac Primary Mortgage Market Survey (30-year and 15-year fixed, weeks of October 8 and 15, 2026, and historical data): https://www.freddiemac.com/pmms and https://www.freddiemac.com/pmms/docs/historicalweeklydata.xlsx (also on FRED: https://fred.stlouisfed.org/series/MORTGAGE30US)
• HUD, Revised FY 2026 Fair Market Rents notice, Federal Register, April 21, 2026: https://www.govinfo.gov/content/pkg/FR-2026-04-21/html/2026-07741.htm ; HUD USER Fair Market Rents: https://www.huduser.gov/portal/datasets/fmr.html
• California Department of Housing and Community Development, ADU Handbook (March 2026): https://www.hcd.ca.gov/sites/default/files/docs/policy-and-research/adu-handbook-update.pdf ; ADU page: https://www.hcd.ca.gov/policy-and-research/accessory-dwelling-units
• California Government Code sections 66314, 66315, 66316, 66317, 66321, 66323, 66333, 66340, and 66341 (official text at https://leginfo.legislature.ca.gov/; text consulted at https://california.public.law/codes/government_code_section_66314 and the corresponding pages for each section); sections 66311.5, 66311.7, 66322, and 66342 as summarized in the HCD ADU Handbook
• City of Los Angeles Department of Building and Safety, Accessory Dwelling Unit (ADU): https://dbs.lacity.gov/adu ; ADU Standard Plan Program: https://dbs.lacity.gov/adu/approved-standard-plans
• LA County Planning, Accessory Dwelling Units: https://planning.lacounty.gov/planning-permits/accessory-dwelling-units/ ; Standard ADU Plans Program, County Catalog: https://planning.lacounty.gov/planning-permits/accessory-dwelling-units/county-catalog/ ; Standard ADU Plan A sheets: https://planning.lacounty.gov/wp-content/uploads/2024/10/adu_standard_plan_a.pdf ; Fire-rebuild Standard Plan Catalog: https://planning.lacounty.gov/disaster-recovery/pre-approved-standard-plans/standard-plan-catalog/
• LA County Public Works, Building and Safety, Pre-Approved ADU Standard Plans: https://pw.lacounty.gov/building-and-safety/adu/pre-approved
• Los Angeles County Assessor, New Construction: https://assessor.lacounty.gov/homeowners/new-construction ; Real Property: https://assessor.lacounty.gov/homeowners/realproperty ; ADU: https://assessor.lacounty.gov/homeowners/adu
• California Legislature, SB 1164 (2023-2024) bill history: https://leginfo.legislature.ca.gov/faces/billHistoryClient.xhtml?bill_id=202320240SB1164
• Fannie Mae Selling Guide Announcement SEL-2025-08 (October 8, 2025): https://singlefamily.fanniemae.com/media/43851/display ; Selling Guide B3-3.8-02, Rental Income from the Subject Property: https://selling-guide.fanniemae.com/sel/b3-3.8-02/rental-income-subject-property ; Selling Guide B2-3-04, Special Property Eligibility Considerations: https://selling-guide.fanniemae.com/sel/b2-3-04/special-property-eligibility-considerations ; Fannie Mae ADU financing page: https://singlefamily.fanniemae.com/originating-underwriting/mortgage-products/accessory-dwelling-units ; DU release notes: https://singlefamily.fanniemae.com/media/44631/display
• Freddie Mac, Accessory Dwelling Units fact sheet (February 2026): https://sf.freddiemac.com/docs/pdf/fact-sheet/adu-fact-sheet.pdf
• HUD, FHA Mortgagee Letter 2023-17, Revisions to Rental Income Policies, Property Eligibility, and Appraisal Protocols for Accessory Dwelling Units: https://www.hud.gov/sites/dfiles/OCHCO/documents/2023-17hsgml.pdf
• FHFA, Conforming Loan Limit Values for 2026: https://www.fhfa.gov/data/conforming-loan-limit
• California Civil Code section 1947.12: https://california.public.law/codes/civil_code_section_1947.12