Homeowners ask us the same question in almost every ADU consultation: will the rent cover what the unit costs to build? This page puts two public numbers side by side so you can answer it for your own lot: what an ADU typically costs to build in Southern California, using the same budgeting ranges we publish across this site, and what a unit of that size rents for, using the U.S. Department of Housing and Urban Development’s Fair Market Rents for fiscal year 2026. Everything here is an estimate, not a quote and not financial advice; the point is to show the order of magnitude before you spend money on drawings.
What an ADU rents for: HUD Fair Market Rents, FY 2026
HUD publishes a Fair Market Rent for every metro area each fiscal year. It is the 40th-percentile gross rent (rent plus utilities) for a modest, recently rented unit, so roughly 40 percent of comparable rentals lease for less and 60 percent for more. It is the figure the Section 8 program pays against, and it is a conservative benchmark for a new, well-finished ADU. The FY 2026 figures below took effect on 1 October 2025.
| Area (HUD FMR area) | Studio | 1-bedroom | 2-bedroom |
|---|---|---|---|
| Los Angeles County (Los Angeles-Long Beach-Glendale) | $1,863 | $2,085 | $2,601 |
| Orange County (Santa Ana-Anaheim-Irvine) | $2,682 | $2,746 | $3,236 |
| Ventura County (Oxnard-Thousand Oaks-Ventura) | $1,998 | $2,250 | $2,693 |
| Riverside and San Bernardino counties (Riverside-San Bernardino-Ontario) | $1,692 | $1,777 | $2,201 |
Build cost against rent: simple payback by ADU type
The table divides our published Southern California budgeting range for each ADU type by twelve months of the Los Angeles County Fair Market Rent for a unit of that size. “Simple payback” means years of gross rent needed to equal the build cost, before vacancy, taxes, insurance, maintenance, management or loan interest. It is a screening number, not a return on investment.
| ADU type | Typical build cost (our budgeting range) | Rent benchmark (LA County FMR) | Gross rent per year | Simple payback |
|---|---|---|---|---|
| Garage conversion, studio | $100,000–$200,000 | $1,863 / month | $22,356 | 4.5–8.9 years |
| Garage conversion, 1-bedroom | $100,000–$200,000 | $2,085 / month | $25,020 | 4.0–8.0 years |
| Detached ADU, about 500 sq ft, 1-bedroom | $180,000–$260,000 | $2,085 / month | $25,020 | 7.2–10.4 years |
| Detached ADU, 700–800 sq ft, 2-bedroom | $225,000–$350,000 | $2,601 / month | $31,212 | 7.2–11.2 years |
| Detached ADU, about 1,000 sq ft, 2-bedroom | $300,000–$450,000 | $2,601 / month | $31,212 | 9.6–14.4 years |
Two things stand out. A garage conversion is the fastest to pay back because the slab, walls and roof already exist, which is why so many San Fernando Valley ADUs start as garage conversions. And the jump from a 500 sq ft one-bedroom to an 800 sq ft two-bedroom adds roughly $500 a month of rent at the Los Angeles benchmark but $45,000 to $90,000 of cost, so the larger unit pays back over a similar or slightly longer period; it makes more sense when a two-bedroom suits the household or the lot than as a pure income play.
The same math in Orange, Ventura, Riverside and San Bernardino counties
| Area | 1-bedroom FMR | Detached 500 sq ft ADU ($180,000–$260,000): payback | 2-bedroom FMR | Detached 700–800 sq ft ADU ($225,000–$350,000): payback |
|---|---|---|---|---|
| Los Angeles County | $2,085 | 7.2–10.4 years | $2,601 | 7.2–11.2 years |
| Orange County | $2,746 | 5.5–7.9 years | $3,236 | 5.8–9.0 years |
| Ventura County | $2,250 | 6.7–9.6 years | $2,693 | 7.0–10.8 years |
| Riverside and San Bernardino counties | $1,777 | 8.4–12.2 years | $2,201 | 8.5–13.3 years |
What the simple payback leaves out
- Vacancy and turnover. Budget for at least a few weeks empty between tenants and for repainting and repairs at turnover.
- Property tax. In California the new construction is assessed and added to your tax bill; the existing house is not reassessed. Ask the county assessor how they value ADUs before you build.
- Insurance, utilities and maintenance. A rented ADU usually means a landlord policy and, if the unit is not separately metered, utilities you pay and recover through rent.
- Financing. Interest changes the picture more than any other line. Our ADU financing options guide compares HELOCs, cash-out refinances, renovation loans and construction loans, and explains how some lenders count expected ADU rent toward qualifying.
- Rent rules. State law requires ADU leases of longer than 30 days, so short-term rental income is not part of this math. Local rent regulations may apply to the unit; check with the city before setting expectations.
- Resale value. The unit adds value at sale as well as rent, but appraisers value ADUs inconsistently. Treat resale as upside, not as part of the payback.
What changes the answer on your lot
The cost side moves more than the rent side. A garage with a sound slab and a 200-amp panel nearby sits at the bottom of the range; a detached unit on a hillside lot, in a fire zone, or with a long sewer run to the street sits at the top. What your city lets you build sets the size, and size sets the rent: use the city-by-city ADU rules table or the California ADU rules calculator to see whether a 500 sq ft one-bedroom or an 800 sq ft two-bedroom is realistic on your lot, then read how long an ADU takes, because months of design and permitting are months without rent.
How we estimated these numbers
Rent benchmarks are HUD’s published FY 2026 Fair Market Rents for the four metro areas we work in, unchanged. Build costs are Green Design and Build’s own Southern California budgeting ranges, drawn from our written proposals and completed projects and checked against current supplier and subcontractor pricing; they are estimates, not a price list, and a real project can come in lower or higher. Payback is build cost divided by twelve months of gross rent, with nothing else deducted. Reviewed by Dekel Sofer, licensed general contractor (CSLB #1110975), September 2026. Publishers and journalists are welcome to cite these figures with a link to this page. This page is general information, not financial, tax or legal advice.
ADU rental income FAQs
How much rent can an ADU earn in Los Angeles?
HUD’s FY 2026 Fair Market Rent for Los Angeles County is $1,863 for a studio, $2,085 for a one-bedroom and $2,601 for a two-bedroom, including utilities. A new ADU in a strong neighborhood often rents above those figures; the FMR is a conservative benchmark, not a ceiling.
Which ADU pays for itself fastest?
A garage conversion, because the structure already exists: at $100,000 to $200,000 against a one-bedroom benchmark rent of $2,085 a month in Los Angeles County, the simple payback is roughly four to eight years of gross rent, before expenses.
Can I rent my ADU on Airbnb?
Not under state ADU law, which requires rentals of longer than 30 days. Cities enforce this through the ADU permit conditions.
Will building an ADU raise my property taxes?
The new construction is assessed and added to your bill; the existing home keeps its current assessment. The county assessor can tell you how they value ADUs, and a tax professional can tell you how the rent and the new assessment interact for you.
Get real numbers for your lot
A two-hour site visit tells us which unit your lot can take, where the sewer and panel are, and what the realistic budget is; a written proposal follows within 48 hours. Book a free consultation or read more about how we design and build ADUs across Southern California.