What Buyers, Sellers, and the Next 6 Months Look Like
Every month I look at every Costa Mesa home for sale that has an ADU. An ADU is a second, smaller home on the same lot. Some people call it a granny flat or a back house. Many owners rent it out. Some use it for family.
This report is for everyone. If you want to buy, I’ll show you where the deals are. If you want to sell, I’ll show you what is selling and what is not. At the end, I’ll tell you what I think the next six months will look like.
Here is the short version: homes with a rented ADU and a fair price sold fast. Homes priced too high are cutting their price. And mortgage rates just went up. That changes things for everyone.
Last month, I covered two Costa Mesa ADU homes that had just gone into escrow. Both closed in September. And every home from last month’s list that did not sell has now cut its price. Let’s look at why.
The Quick Numbers
| What we counted | The number |
|---|---|
| ADU homes for sale right now | 7 |
| Price range | $1,600,000 to $3,399,999 |
| Middle (median) asking price | $2,200,000 |
| Middle days on the market | 35 days |
| Homes with a price cut | 4 of 7 |
| Homes sold in September | 2 |
| Sold prices | $1,975,000 and $3,400,000 |
| ADU rents on listed and sold homes | $3,500 to $5,750 a month |
| 30-year mortgage rate (Oct. 1) | 7.28% |
Data: CRMLS listings with an ADU in Costa Mesa, pulled October 2, 2026. Mortgage rate from Freddie Mac’s weekly survey.
Costa Mesa ADU homes cost more than a typical Costa Mesa home. The middle asking price is $2.2 million. For the whole city, the middle sale price of all homes was about $1.57 million in August, according to Redfin. That is a gap of about $630,000. That makes sense. You are buying two places to live on one lot, close to the beach.
The Homes for Sale Right Now
Here are all 7 ADU homes for sale in Costa Mesa, from lowest to highest price.
| Address | Price | Beds / baths | ADU size | ADU rent | Days listed |
|---|---|---|---|---|---|
| 544 Bernard St | $1,600,000 | 5 bed / 3 bath | 510 sq ft | Not rented | 11 |
| 1430 Shamrock | $1,839,000 | 3 bed / 2 bath | 325 sq ft | Not rented | 43 |
| 278 Santo Tomas | $1,849,000 | 4 bed / 2.5 bath | About 590 sq ft | Rented | 24 |
| 1822 Pomona | $2,200,000 | 5 bed / 4 bath | 1,200 sq ft (built 2026) | $5,000/mo | 18 |
| 2049 Monrovia | $2,325,000 | 4 bed / 4 bath | 1,100 sq ft (built 2022) | Not rented | 35 |
| 3097 Molokai Pl | $2,915,000 | 3 bed / 2 bath main, plus 2 bed / 2 bath ADU | 986 sq ft (built 2024) | Not rented (about $3,500/mo expected) | 92 |
| 1578 San Bernardino | $3,399,999 | 6 bed / 5.5 bath | About 1,000 sq ft | Not rented (about $3,500/mo expected) | 68 |
A few things jump out:
- Four homes cut their price. 3097 Molokai dropped from $2,995,000 to $2,915,000. 1430 Shamrock dropped from $1,889,000 to $1,839,000. 2049 Monrovia dropped from $2,375,000 to $2,325,000. 1578 San Bernardino dropped from $3,500,000 to $3,399,999. The cuts ranged from $50,000 to $100,000.
- Two homes have been listed a long time. 3097 Molokai has been for sale for 92 days. That is about three months. 1578 San Bernardino is at 68 days.
- The cheapest home is a project. 544 Bernard is being sold by a court-appointed receiver, as-is. It needs a lot of work, and the buyer has to sign an agreement with the City of Costa Mesa to finish the remodel. Traditional loans will not work here. This one is for cash buyers who know construction.
- Only one home has a rented ADU, and it is the newest. The brand-new 1,200 sq ft ADU at 1822 Pomona rents for $5,000 a month on a one-year lease. Most of the other ADUs are empty. That means buyers have to guess at the rent, and that makes the price harder to accept.
Sold in September (2 homes)
| Address | Asking price | Sold price | Days | How it went |
|---|---|---|---|---|
| 247 23rd St | $3,250,000 | $3,400,000 | 5 | Sold $150,000 over asking. All cash. The 1,187 sq ft ADU is rented for $5,750 a month. |
| 1697 Labrador | $1,999,999, then cut to $1,899,999 | $1,975,000 | 34 | Sold over the lowered price, but $24,999 under the first price. The seller also paid $34,000 toward the buyer’s repairs and closing costs. The ADU is about 420 sq ft and attached. |
Here is the lesson. The home with a big, detached ADU and a renter already paying $5,750 a month sold in 5 days for $150,000 over asking. The home with a small attached unit had to cut its price, took 34 days, and the seller still paid part of the buyer’s costs. After that $34,000 credit, the seller took home about the same as the lowered price.
Both are good homes. The difference was the ADU. Buyers will pay more for a bigger back house that already earns rent.
The Buyer’s Side of the Story
If you want to buy, this is a better month for you than last month. Here’s why.
1. You have more room to ask. Four out of seven sellers have already cut their price. One September seller paid $34,000 of the buyer’s costs. Sellers are more open to a deal than they were this summer.
2. Look at homes that have been sitting. If a home has been for sale for 60 or 90 days, the seller is likely ready to talk. You can ask for a lower price. You can ask the seller to pay some of your costs. You can ask for repairs.
3. Don’t expect a deal on every home. The best homes still get bid up fast. 247 23rd St sold $150,000 over asking in five days. If you find a fairly priced home with a big, rented ADU, be ready to move quickly.
4. Rates went up, so the rent matters more. The average 30-year rate hit 7.28% this week. A year ago it was 6.34%. On a $1.76 million loan, that is about $1,100 more a month. That’s why ADU rent is so helpful. Take 1822 Pomona. The ADU rents for $5,000 a month. With 20% down, the loan payment is about $12,040 a month. The back house covers about 4 of every 10 dollars of that payment. Some lenders can even count ADU rent to help you qualify for a loan.
5. Check the paperwork. Before you buy, make sure the ADU was built with permits from the city. Ask for the permits, the lease, and the utility details. Here is my list of the documents you should get during escrow on an ADU home. One more Costa Mesa rule to know: the city does not allow short-term rentals, so plan on a long-term tenant, not Airbnb.
The Seller’s Side of the Story
If you want to sell, here is the honest truth: price and proof of rent are everything right now.
1. Buyers are picky. They can see which homes have been sitting and which ones cut their price. They will skip a home that feels overpriced, even a nice one.
2. Price it right the first time. Every home from last month’s list that did not sell has now cut its price. 1697 Labrador started too high, cut its price, and still paid $34,000 of the buyer’s costs. Cutting your price later often costs you more than pricing right on day one.
3. Your ADU rent is your best selling point. Buyers are paying higher rates. Monthly cash matters to them. The fastest sale this month had a tenant paying $5,750 a month. If your ADU is rented, show the lease and the rent. If it is empty, show what it could rent for with real local numbers.
4. Have your permits ready. Have your permit papers and final sign-off ready before you list. Buyers and their lenders will ask. If you have a tenant, plan ahead for showings. Here is how to sell an ADU home with a tenant living there. For the full step-by-step, see my seller’s guide to selling a home with an ADU.
5. Be ready to help the buyer. Offering a credit can work better than a big price cut. It lowers the buyer’s cash needed at closing, or it can pay to bring their rate down. That matters a lot when rates are over 7%.
What to Expect in the Next 6 Months
Here is what I expect from now through March 2027. This is my best guess, not a promise.
October to December: slower, with more deals. Fall and the holidays are always slower. Fewer people move. Rates are near their highest point in about three years. I expect more price cuts on homes over $2.5 million, and more sellers paying part of the buyer’s costs.
Homes with big, rented ADUs will still sell fast. There are only 7 ADU homes for sale in the whole city. When one shows up with a fair price and a tenant already paying rent, buyers jump. I don’t see that changing.
January 2027: two new state laws start. Governor Newsom just signed AB 956 and SB 1117. Starting January 1, 2027, many single-family lots can add two new detached ADUs instead of one. Fees for ADUs over 750 sq ft also go down. Here is how the fee change works in Costa Mesa and the rest of OC. This could make Costa Mesa’s bigger lots, like those in Mesa Verde and the Eastside, worth more to builders and investors. You can read the state’s ADU rules on the California HCD ADU page, and Costa Mesa’s own rules on the city’s ADU page.
February to March 2027: spring buyers come back. Spring is when most buyers shop. If rates come down even a little, more buyers will return and prices could firm up. If rates stay high, prices will likely stay flat, and fair pricing will still matter most.
My simple advice:
- Buyers: Fall and winter are your window. Fewer people are shopping. Sellers are more open to deals.
- Sellers: If you want top dollar, price right now, or get ready to list in early spring with permits, a lease, and rent numbers in hand.
Want to compare? See how Anaheim ADU homes are doing this October, or look back at Costa Mesa in September.
Find Your Costa Mesa ADU Home
Want to see every home with an ADU for sale in Orange County? The list updates on its own as new homes hit the market.
👉 Search Orange County homes with ADUs here
Related Reading
Have a question about a home on this list? I am happy to help you check the permits, the rent, and the numbers before you make an offer.
Dylan Serna, The ADU Realtor
eXp Realty | DRE #02217359
dylan@serna-realestate.com
Data from CRMLS as of October 2, 2026, deemed reliable but not guaranteed. Payment examples use 20% down and a 30-year loan, principal and interest only, and do not include taxes or insurance. This is not financial advice.
