Short answer: Garden Grove is the best city in Orange County for ADU investing in 2026. It has the most ADUs built of any OC city, entry prices near $1.1 million, ADU rents of $2,350 to $3,800 a month, and the deepest pool of ADU sales for appraisers to lean on. Anaheim is a close second. Westminster has the strongest rents for the price, Santa Ana has the lowest entry point, and Costa Mesa is the long-term appreciation play.
But “best” depends on what you want the property to do. A buyer chasing monthly cash flow should not buy the same city as a buyer who wants to hold for 20 years and sell to a high-income owner-occupant. So below I show the data, the math, and which city fits which goal.
Every price and rent here comes from my monthly CRMLS pulls of homes with ADUs (September and October 2026), plus state and university data on where ADUs actually get built.
The 4 Things That Make a City Good for ADU Investing
I score Orange County cities on four factors. Most investors only look at the first one.
- Entry price. What it costs to buy a house with a buildable lot or an existing ADU.
- ADU rent. What second units are actually leasing for on current listings, not what a calculator guesses.
- ADU volume. How many ADUs the city has finaled. High volume means more comps for your appraisal, more contractors who know the city’s plan check, and a building department that has done this hundreds of times.
- City rules. Rent caps, short-term rental bans, and whether the city’s ADU ordinance fights state law.
Where Orange County Actually Builds ADUs
This is the data point most “best city” lists skip. Cal State Fullerton’s Center for Demographic Research tracks every ADU finaled in Orange County. Their 2005 to 2025 ADU report shows that four central-county cities do most of the building:
| City | ADUs finaled 2024 | ADUs finaled 2025 | Total 2005 to 2025 | Share of all OC ADUs |
|---|---|---|---|---|
| Garden Grove | 265 | 244 | 1,722 | 22.3% |
| Anaheim | 222 | 226 | 866 | 11.2% |
| Westminster | 163 | 194 | 752 | 9.8% |
| Santa Ana | 156 | 172 | 723 | 9.4% |
| Orange | 73 | 65 | 357 | 4.6% |
| Huntington Beach | 80 | 89 | 354 | 4.6% |
| Fullerton | 28 | 48 | 304 | 3.9% |
| Costa Mesa | 66 | 70 | 206 | 2.7% |
| All of Orange County | 1,492 | 1,696 | 7,709 | 100% |
Source: CSUF Center for Demographic Research, Table 1, net ADU activity (completed or finaled units), July 2026. Share column calculated from the report’s totals.
Garden Grove alone has built more than one in five ADUs in the county. Garden Grove, Anaheim, Westminster and Santa Ana together account for more than half. That matters for three reasons:
- Appraisals. An appraiser needs closed sales of homes with ADUs to give your ADU value. In a city with 1,700 ADUs, those comps exist. In a city with 50, they often don’t.
- Build speed. Contractors and designers who have pushed dozens of plans through the same city know what plan check will flag.
- Exit. When you sell, buyers in that city already understand what an ADU home is worth.
And the trend is up. Orange County issued 1,916 ADU permits in 2025, about 40% more than in 2024, and more than the 1,459 single-family home permits issued that year, according to Cotality data reported by the Orange County Business Journal.
How Much of the Mortgage Does the ADU Cover?
For an analytical buyer, this is the cleanest way to compare cities. I took each city’s median asking price for homes with ADUs, assumed 20% down and a 30-year loan at 7.28% (the Freddie Mac average on October 1, 2026), and compared the principal and interest payment to the middle of each city’s ADU rent range.
| City | Median ADU-home price | Monthly P&I (20% down) | ADU rents seen | ADU covers about |
|---|---|---|---|---|
| Santa Ana | $1,050,000 | $5,747 | $2,200 to $3,650 | 51% |
| Westminster | $1,675,000† | $9,168 | $3,300 to $4,300 | 41% |
| Fullerton | $1,598,000‡ | $8,747 | $3,500 to $3,650 | 41% |
| Anaheim | $1,449,500 | $7,934 | $2,800 to $3,450 | 39% |
| Costa Mesa | $2,200,000 | $12,042 | $3,500 to $5,750 | 38% |
| Garden Grove | $1,549,500 | $8,481 | $2,350 to $3,800 | 36% |
| Huntington Beach | $2,425,000 | $13,274 | $2,500 to $5,000 | 28% |
†Westminster: middle of the four active ADU listings. ‡Fullerton: median of the five homes in escrow, since only four were active. Principal and interest only. Taxes, insurance and maintenance are not included. Prices from CRMLS, September to October 2026.
Two things stand out. First, most of the core cities land in the same 36% to 41% band, so rent alone doesn’t separate them. Second, Garden Grove looks weaker on asking prices than it does on closed sales. Its median sold price in September was $1,120,000, more than $400,000 below the median ask. At that price, the same ADU rent covers about half the payment. In Garden Grove, the deals are being made on the smaller, fairly priced homes, and the big listings are sitting.
This is why lenders care so much about ADU rent right now. With rates above 7%, some loan programs let you count part of that rent to qualify. I ran the numbers on how much more house ADU income can help you qualify for.
The Best Orange County Cities for ADU Investing, by Goal
Best overall: Garden Grove
Garden Grove wins because it scores well on all four factors at once. Big lots, many with room for a detached ADU. Entry near $1.1 million on closed sales. Newer 1,200 sq ft ADUs renting for $3,200 to $3,800. And the most ADUs of any city in the county, which means the deepest comp pool for your appraisal.
In September, the two lowest-priced ADU homes sold in five days for more than asking. Homes priced over $1.5 million are cutting price or sitting for 100 to 189 days. The full list is in my October Garden Grove ADU market report, and I show the buy-and-build math from purchase to first rent check in my Garden Grove case study on a $1.05M purchase.
One thing to watch: in March 2026, the state housing department sent Garden Grove written findings that parts of its ADU ordinance don’t fully comply with state ADU law, including minimum unit sizes and some setback and design rules. For an investor, that is mostly good news. It means the state is pushing the city toward the more permissive state standards. But it also means your designer needs to know which version of the rules plan check is applying.
Runner-up: Anaheim
Anaheim is the second-biggest ADU city in the county, with 226 finaled in 2025. It gives you the widest range of choices: eight ADU homes for sale in October, from $968,000 to $1,840,000, with a median ask of $1,449,500. Two-bedroom ADUs on current listings rent for $2,800 and $3,450.
Half the Anaheim listings have been on the market more than two months, so buyers have room to negotiate. The risk is permits. Several listings this fall noted unknown permit status on a room or unit. Before you buy, read how AB 2533 changes the math on an unpermitted ADU. Every listing is in my Anaheim October report.
Best rent for the price: Westminster
Westminster finaled 194 ADUs in 2025, the third most in the county, and its second units rent for about $3,300 to $4,300 a month. That’s at or above Garden Grove and Anaheim on comparable lots.
This fall, it’s also the clearest buyer’s market of the group. A fairly priced three-unit lot went into escrow in about two weeks, while overpriced homes took price cuts from $50,000 up to $688,000. See the Westminster fall ADU report.
Lowest entry and highest coverage: Santa Ana
Santa Ana has the lowest entry point in Orange County. ADU homes start under $900,000, and the median ask was $1,050,000 in my September pull. That’s why the ADU covers about half the mortgage payment, the best ratio in the county.
The catch is rent growth. Santa Ana’s rent stabilization ordinance caps annual increases at 2.87% from September 2026 through August 2027 on covered units. A cap like that limits how fast your income can grow over a 10-year hold, so confirm whether your specific units are covered before you buy. I break down the long-term effect in what Santa Ana’s 2.87% rent cap means for your ROI.
Best appreciation play: Costa Mesa
Costa Mesa is not a cash flow city. It’s where high-income owner-occupants pay up to live near the coast. The median ADU home asks $2.2 million, and ADU rents are the highest in the group, $3,500 to $5,750 a month. In September, a home with a 1,187 sq ft ADU rented at $5,750 sold in five days, $150,000 over asking, all cash.
Two limits: Costa Mesa only finaled 70 ADUs in 2025, so comps are thinner, and the city bans short-term rentals, so every number has to work on a long-term tenant.
Cities I’d approach with caution
- Huntington Beach. Median ask around $2.4 million, and the ADU covers only about 28% of the payment. Both recent sales closed under asking.
- Fullerton. Strong ADU rents ($3,500 to $3,650), but only 48 ADUs finaled in 2025. Thin comps make appraisals harder to predict.
- Yorba Linda, Cypress, Stanton. Very few ADU sales, which means unpredictable appraisals and fewer buyers when you sell.
The Build Math Is Similar Everywhere. The Rent Is Not.
Here’s a point a lot of investors miss: building an ADU costs about the same in Garden Grove as it does in Costa Mesa. In my breakdown of what it really costs to buy a home and add an ADU in Orange County, an 850 sq ft, 2 bed, 2 bath detached ADU comes in around $260,000 all in, including design, permits, school fees and utilities.
At that cost, every $500 a month of extra rent adds about 2.3 percentage points of yield on the build. A $3,000 ADU returns about 13.8% gross on $260,000. A $3,500 ADU returns about 16.2%. So the city doesn’t change your build cost much. It changes your rent, your purchase price and your exit. That’s why the lot you buy matters more than the ADU you build.
And the rules are about to get better. Starting January 1, 2027, AB 956 lets many single-family lots add two detached ADUs instead of one, and SB 1117 removes the city impact fee on the first 750 sq ft. Big-lot cities like Garden Grove, Anaheim and Westminster gain the most. The state’s full rules are on the California HCD ADU page.
So Which City Should You Buy In?
| If your goal is… | Start with | Why |
|---|---|---|
| Best all-around ADU investment | Garden Grove | Most ADUs built, deep comps, entry near $1.1M |
| Most choices and room to negotiate | Anaheim | 8 listings, half sitting 60+ days |
| Highest rent for the price | Westminster | $3,300 to $4,300 second-unit rents |
| Lowest cash in, best payment coverage | Santa Ana | Entry under $900K, ADU covers about 51% |
| Long-term appreciation | Costa Mesa | Top rents, coastal buyers, thin comps |
Frequently Asked Questions
What is the best city in Orange County for ADU investing? Garden Grove, based on fall 2026 data. It has built more ADUs than any other OC city (1,722 through 2025, about 22% of the county), closed ADU-home sales between $1.02 million and $1.2 million in September, and ADU rents up to $3,800 a month.
Which Orange County city builds the most ADUs? Garden Grove, followed by Anaheim, Westminster and Santa Ana. Together those four cities account for more than half of all ADUs finaled in Orange County from 2005 to 2025, according to Cal State Fullerton’s Center for Demographic Research.
What is the cheapest city in Orange County to buy a home with an ADU? Santa Ana. ADU homes start under $900,000, and the median ask was about $1,050,000 in September 2026. Check the city’s rent stabilization rules before you buy.
How much do ADUs rent for in Orange County? On fall 2026 listings, about $2,200 to $3,800 a month in central OC cities like Garden Grove, Anaheim and Santa Ana, $3,300 to $4,300 in Westminster, and up to $5,750 in Costa Mesa. Size, bedroom count and age drive most of the difference.
How much does it cost to build an ADU in Orange County? About $250,000 to $290,000 all in for a typical 850 sq ft, 2 bed, 2 bath detached ADU, including design, permits, school fees and utility work. Garage conversions cost less.
Does an ADU pay for itself in Orange County? Not fully, at today’s rates. In most core OC cities, the ADU rent covers about 36% to 41% of the principal and interest on a home with an ADU at 20% down. In Santa Ana it covers about half.
Get the Numbers on a Specific Lot
The city narrows the search. The lot decides the deal. If you want me to run the purchase price, build cost, rent and payment coverage on a specific property, or find lots in these cities that fit the ADU you want to build, call Dylan Serna, ADU Realtor at 714-860-2868.
Dylan Serna, The ADU Realtor | eXp Realty | DRE #02217359 | dylan@serna-realestate.com
This post is general information, not financial or investment advice. Prices and rents come from CRMLS listings pulled in September and October 2026 and change constantly. Payment examples use 20% down, a 30-year fixed loan at 7.28%, principal and interest only. ADU counts are net completed units from the CSUF Center for Demographic Research.
