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Orange County: How to Buy a Home With an ADU, or Room for Two, Before the 2027 Rules Arrive (November 2026)

By Dr. Hamid Rowshan, Choice of America

How to buy an Orange County home with an ADU or room for two: check permits and the 2027 rules, ask the city and your lender, run the rent math and negotiate.

A backyard unit has become one of the most practical tools Orange County buyers have: a place for a parent, a grown child, or a tenant whose rent helps carry the mortgage. The rules are changing again, and this fall's local news shows why it matters to anyone shopping for a single-family home:

  • Huntington Beach council sides with two backyard units. At its October 20, 2026 meeting, the Huntington Beach City Council heard an appeal of the Planning Commission's denial of Coastal Development Permit 26-006 for two detached ADUs at 205 Pecan Avenue. According to Citizen Portal's meeting report the same day, the council reversed the commission's earlier 4–2 denial and approved the permit on a 6–0–1 vote, after city staff said the units complied with state ADU law and did not reduce existing parking.
  • Two detached ADUs per lot starting January 1, 2027. Governor Newsom signed AB 956 (Quirk-Silva) on September 29, 2026 (Chapter 791, Statutes of 2026). It requires cities to approve, ministerially, two detached, new-construction ADUs on a lot with an existing or proposed single-family home, up from one, with 4-foot side and rear setbacks. Cities may cap each at 800 square feet of livable space. The same day he signed SB 1117 (Chapter 809), which says that, for up to two ADUs on a lot, any impact fee on an ADU larger than 750 square feet may be charged only on the area above 750 square feet.
  • Cities are under pressure to add housing. Voice of OC reported on October 30 that Huntington Beach now owes more than $160,000 in court-ordered penalties over its housing plan, with $50,000 more each month until it complies. On October 20, Voice of OC, citing a state housing database, reported that Costa Mesa has permitted more than 550 of the 11,760 homes it must plan for by 2029, under 5%.

None of this means every lot can hold two new cottages. It means the ADU question now belongs at the start of your home search, not after you move in. Here is how to buy a home with an ADU, or with real room for one or two, step by step.

The market snapshot (September 2026, Realtor.com)

Realtor.com's October 2026 county figures had not been released as of November 2, so September 2026 is the latest month.

Measure (Orange County)September 2026Change vs. Sep 2025
Median listing price$1,287,500−6.5%
Active listings4,735+3.9%
New listings2,114+1.2%
Median days on market53−6.2%
Price-cut share (Realtor.com price_reduced_share)21.1%+3.7 points
Pending listings1,655−18.4%
Median listing price per square foot$704−2.8%

Source: Realtor.com Residential Data, county inventory core metrics, September 2026 (also published by FRED as series MEDLISPRICOU6059, ACTLISCOU6059, NEWLISCOU6059, MEDDAYONMARCOU6059 and PENLISCOU6059). The price-cut share is Realtor.com's own price_reduced_share.

Pending listings down 18.4% with active listings up 3.9% means fewer buyers are signing contracts while more homes sit on the market. More than one listing in five had a price cut in September. That's useful leverage when you're asking a seller about an unpermitted garage conversion or a lot that needs work before it can hold an ADU.

Where ADU-friendly lots are listed: a ZIP-code look

Older tract neighborhoods with deeper lots, alleys or detached garages are often where ADUs fit most easily. These are Realtor.com's September 2026 figures for a sample of Orange County ZIP codes. ZIP medians include condos and townhomes, so they're a starting point, not a price for a house with a big yard.

ZIP (city)Median listing priceChange vs. Sep 2025Days on marketPrice-cut shareActive listingsMedian sq. ft.
92648 (Huntington Beach)$1,680,750−3.2%5721.1%972,051
92626 (Costa Mesa)$1,572,444−7.1%4822.2%451,747
92843 (Garden Grove)$986,250−3.1%5215.2%181,235
92804 (Anaheim)$958,475+3.5%5615.1%551,425
92780 (Tustin)$899,225−7.7%5120.2%471,387
92805 (Anaheim)$865,000−1.0%5022.8%761,447
92704 (Santa Ana)$799,225+15.1%5720.8%541,200
92831 (Fullerton)$729,000−3.4%4714.4%361,330

Source: Realtor.com Residential Data, ZIP inventory core metrics, September 2026. ZIPs that Realtor.com flagged as less reliable that month are left out.

What the law now allows, in plain words

Today (through December 31, 2026). On a lot with a single-family home, state law already requires a city to approve one ADU plus one junior ADU (JADU) inside the existing house or an existing accessory structure, plus one detached new-construction ADU, if the units meet the state standards (Government Code Section 66323).

From January 1, 2027 (AB 956). The detached allowance doubles to two new-construction detached ADUs, each of which a city may cap at 800 square feet and at the state height limits, with side and rear setbacks of no more than 4 feet. A city does not have to approve a JADU on a lot where two detached ADUs have been built.

Rules that stay the same and matter to buyers:

  • No short-term rentals for these units. Cities must require that rentals of ADUs approved this way be for longer than 30 days. Don't plan on nightly-rental income.
  • HOAs can't flatly ban them. Under Civil Code Section 4751, HOA rules that prohibit or unreasonably restrict an ADU or JADU on a lot zoned to allow single-family homes are void, though "reasonable restrictions" are still allowed. AB 956 widened that wording from lots "zoned for" single-family use to lots "zoned to allow" it.
  • Fees. No impact fees on an ADU of 750 square feet or less (or a JADU of 500 or less). From January 1, for up to two ADUs on a lot, impact fees on a larger ADU apply only to the area above 750 square feet (SB 1117). Utility connection fees and school fees are separate; ask the water district and school district.
  • Sprinklers. An ADU can't be required to have fire sprinklers if the main house isn't required to have them.
  • Coastal zone. Near the coast, an ADU can also need a coastal development permit, as at 205 Pecan Avenue in Huntington Beach. That adds a hearing step and time.

Unincorporated areas. For homes in unincorporated Orange County, OC Development Services offers six pre-approved detached ADU plans from a 393-square-foot studio to a 1,200-square-foot three-bedroom (558, 748, 800 and 972 square feet in between). The county says the plans reflect the 2022 California Building Code and are being updated to the 2025 code.

How lenders count ADU rent

This is where many buyers get surprised. Fannie Mae's Selling Guide (B3-3.8-02, dated September 2, 2026) lets a lender count rent from an ADU on a one-unit primary residence, but with limits:

  • Only rent from one existing ADU can be counted, and only on a purchase or a limited cash-out refinance.
  • The lender uses 75% of the gross rent, supported by the appraiser's comparable rent schedule (Form 1007) and, if a tenant is staying, the signed lease.
  • ADU rent can't be more than 30% of your total qualifying income.
  • Fannie Mae's property rules (B2-3-04) allow only one ADU on a one-unit property. The ADU must have its own entrance, kitchen (with a stove or stove hookup), sleeping area and bathroom. Whether a property is a "home with an ADU" or a two-to-four-unit property depends on things like separate meters, a separate address and whether the unit can legally be rented; the appraiser decides.

That last point matters for 2027. A house with two ADUs may not be treated as a one-unit home with an ADU, which can change the loan program, the down payment and the loan limit. Ask your lender before you buy a property with two units in back, or before you plan to build the second.

The payment math at 7.24%

Freddie Mac's 30-year fixed average was 7.24% for the week of October 29, 2026, the latest weekly survey as of today. The monthly principal and interest (P&I) formula is:

P&I = L × i ÷ (1 − (1 + i)^−n)

where L is the loan amount, i is the yearly rate divided by 12 (0.0724 ÷ 12 = 0.006033), and n is 360 months. At 7.24%, that works out to about $6.82 a month for every $1,000 borrowed.

Home (median listing price, 20% down)LoanP&I at 7.24%Property tax at a rough 1.1% a year
County median, $1,287,500$1,030,000$7,019about $1,180 a month
Fullerton 92831, $729,000$583,200$3,974about $668
Santa Ana 92704, $799,225$639,380$4,357about $733
Anaheim 92805, $865,000$692,000$4,716about $793
Tustin 92780, $899,225$719,380$4,903about $824
Garden Grove 92843, $986,250$789,000$5,377about $904
Huntington Beach 92648, $1,680,750$1,344,600$9,163about $1,541

The county-median loan of $1,030,000 is under Orange County's 2026 one-unit conforming limit of $1,249,125. The Huntington Beach loan is above it and would be a jumbo loan. Your real tax rate is on the county tax bill and can include special assessments; insurance and any HOA dues come on top.

What an ADU's rent can offset. HUD's fiscal year 2026 Fair Market Rents for Orange County (the Santa Ana-Anaheim-Irvine area) are $2,682 for a studio, $2,746 for a one-bedroom and $3,236 for a two-bedroom. These are gross rents (rent plus utilities) set near the 40th percentile, so they're a conservative yardstick, not an appraisal. Your appraiser's rent schedule is what the lender will use.

Example: county median home, 20% downMonthly
P&I + property taxabout $8,200
Less a one-bedroom ADU rented at HUD's $2,746about $5,454 left to cover
Less a two-bedroom ADU rented at HUD's $3,236about $4,964 left to cover

How the lender sees it. At 75%, $2,746 of rent counts as about $2,060 a month of income. Because ADU rent can be at most 30% of qualifying income, you'd need at least about $4,806 a month of other income for the full $2,060 to count. If you aim for P&I plus tax at 36% of gross income on the county-median home, you'd need about $22,777 a month ($273,300 a year) with no ADU, or about $20,717 a month ($248,600 a year) of your own income with that ADU rent counted. For comparison, Census QuickFacts puts Orange County's median household income at $116,289 (2020–2024, in 2024 dollars) and the median gross rent at $2,434.

If you plan to build. At 7.24% over 30 years, every $100,000 borrowed costs about $682 a month. Your actual construction cost depends on the design, site work, utilities and the builder, so get written bids; use this only to see how a loan payment compares with the rent the unit could bring. Construction loans, HELOCs and cash-out refinances each have their own rates and terms.

How to buy an Orange County home with an ADU, or room for one or two: step by step

Step 1: Decide what the unit is for. A parent, an adult child, a home office or a tenant all lead to different layouts, privacy needs and budgets. Only a rental produces income your lender may count, and only if it's legal and long-term (over 30 days).

Step 2: Pull the public records before you tour. Find the parcel's zoning and lot size on the county assessor and city maps. Check whether it's in the coastal zone, a very high fire hazard severity zone, or a flood zone, and whether it's in an HOA. Each can add steps, though none is an automatic no.

Step 3: If there's already an ADU, prove it's legal. Ask the seller for the building permit, the final inspection sign-off and the certificate of occupancy for the unit. Then ask the city's building records counter to confirm. A garage conversion with no permit can affect the appraisal, your insurance and whether the lender counts the rent.

Step 4: If you want to build, measure the lot against the rules. With 4-foot side and rear setbacks and units of up to 800 square feet, a lot can hold one or two detached ADUs only if there's room once you account for the house, driveway, separation between buildings, utility lines, trees and fire access. Ask an architect or ADU designer for a quick site sketch during your investigation period. In unincorporated areas, compare the lot with the county's pre-approved plans.

Step 5: Ask the city in writing. Email the planning department the address and ask: What ADU ordinance applies today? How will you process a two-detached-ADU application after January 1, 2027? Are there coastal, historic or fire-zone steps? What school, water and sewer fees apply? Many cities are still updating their codes; state law says a local ADU ordinance that conflicts with state law doesn't apply, but the counter's forms and timelines often lag behind.

Step 6: Check the HOA documents. If the home is in an HOA, read the CC&Rs and architectural rules for ADU provisions. A flat ban isn't enforceable on a lot zoned to allow single-family homes, but reasonable rules on design and process can still apply and take time.

Step 7: Talk to your lender about the ADU before you write the offer. Ask: Will you count ADU rent, and how much? Will a home with two units in back be treated as one-unit-with-ADU or as a two-to-four-unit property? What does that do to my down payment and loan limit? Ask the lender to order an appraisal with a comparable rent schedule.

Step 8: Run your own numbers three ways. Use the formula above for (a) the house alone, (b) the house with the existing or planned ADU rented at a conservative rent, and (c) the house with the ADU empty for three months a year. Add real tax, insurance and HOA numbers. If the purchase only works in case (b), it's too tight.

Step 9: Negotiate with what you find. If the existing unit has no permit, ask for a price cut or credit sized to the cost of legalizing it, or for the seller to obtain the permits before closing. If the yard needs a sewer line upgrade or a tree removed before an ADU can fit, get a bid and ask for a credit. With 21.1% of county listings showing price cuts and pending sales down 18.4%, sellers are listening.

Step 10: Protect yourself in the contract. Use the investigation period for the permit search, the site sketch, the city's written answer and the lender's answer. Keep your right to cancel until all four are in, and put the deadline on your calendar.

Step 11: After closing, plan the build or the lease properly. If you build, use a licensed contractor, keep every permit and inspection, and tell your insurer before construction starts and before a tenant moves in. If you rent, use a written lease, follow California tenant law and any local rules, and keep records; that history helps if you refinance later.

Mistakes to avoid

  • Paying extra for an "ADU" that turns out to be an unpermitted garage conversion.
  • Counting on nightly rental income; these units must be rented for more than 30 days.
  • Assuming your lender will count 100% of the rent, or rent from two units. Fannie Mae counts 75% of one existing ADU's rent, capped at 30% of your income.
  • Planning two ADUs without checking whether the lot really fits them after setbacks, driveway and utilities.
  • Assuming a city's website reflects the January 1, 2027 law; ask in writing.
  • Forgetting the coastal permit step near the beach, which can add months.
  • Letting the investigation contingency expire before the city, the lender and the designer have answered.

Quick checklist

  1. Purpose of the unit decided (family, office or long-term rental).
  2. Zoning, lot size, coastal zone, fire zone, flood zone and HOA status checked.
  3. Permits, final inspection and occupancy sign-off for any existing ADU confirmed with the city.
  4. Site sketch showing whether one or two detached ADUs fit.
  5. City's written answer on current rules, 2027 processing and fees.
  6. HOA documents reviewed for ADU rules.
  7. Lender's answer on counting ADU rent and how the property will be classified.
  8. Payment run three ways, including an empty-unit scenario.
  9. Price, credit or seller repair requested based on what you found.
  10. Investigation deadline on your calendar, with the right to cancel kept until everything is in.

What this means day to day

For an Orange County family, a backyard unit can mean a grandparent five steps away instead of a freeway drive, a college graduate who can afford to stay local, or a long-term tenant whose rent covers a real share of the mortgage. Starting January 1, more single-family lots can legally hold two of these units. But the value only shows up if the unit is legal, fits the lot, and is counted the way you expect by your lender and insurer. The buyers who do well are the ones who ask the city, the lender and the designer before they write the offer, not after.

If you're thinking about buying a home with an ADU, or a lot with room for one, in Orange County, call Choice of America at 833-THIS-BROKER (833-842-7465), visit https://choiceofamerica.com/, or see our Orange County page at https://choiceofamerica.com/orange-county-real-estate.html. We'll help you check the permits, ask the right questions of the city and your lender, and run the full monthly cost on any home you're considering.

Dr. Hamid Rowshan, Choice of America. DRE #02004794, company DRE #02240008.

This article is general information, not legal, tax, construction or lending advice. ADU rules vary by city and parcel and change over time; confirm with the city, your lender and licensed professionals before you buy or build. Rents shown are HUD Fair Market Rents used as examples, not appraisals or guarantees. Figures are from the sources below as of the dates shown.

Sources:

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Dr. Hamid Rowshan · DRE #02004794 · Company DRE #02240008 · Orange, LA, Riverside, San Bernardino & San Diego counties.

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