How Much Can an ADU Earn in Southern California?

Updated October 2026

An ADU in the San Gabriel Valley or Los Angeles can reasonably rent for about $2,200 to $3,200 a month, depending on size and location. Whether that pays off depends on what you spend to build it and how you finance it.

The short version

• HUD’s 2027 Small Area Fair Market Rents, in effect since October 2026, put a one-bedroom at about $2,440 in Alhambra (91801), $2,560 in Monrovia (91016) and $2,590 in Pasadena (91104).
• Two-bedrooms run about $3,010 to $3,200 in the same ZIP codes.
• Payback is simple math: all-in cost divided by net annual rent.
• FHA lenders can count 75% of the expected rent from an existing ADU when you qualify for a mortgage.
• Since January 1, 2026, JADUs, and most ADUs, can’t be rented for less than 30 days.

What the rent numbers mean

Fair Market Rents are HUD’s benchmark for housing vouchers. They’re gross rents, utilities included, set near the 40th percentile of local rents for standard units. Treat them as a conservative floor. A new, well-designed unit with its own entry, yard and laundry often rents above them. A studio squeezed behind a garage often doesn’t.

Check comparable listings within a mile of your lot before you set a budget. Rent varies more between neighborhoods than between cities.

How to run your own numbers

• All-in cost: design, engineering, permit and utility fees, construction, and a contingency.
• Net rent: monthly rent × 12, minus vacancy, insurance, maintenance and the added property tax on the new unit.
• Payback: all-in cost ÷ net annual rent.

Example only: if a unit costs $300,000 all in and nets $24,000 a year, it pays back in about 12.5 years. That’s before financing costs and before any added resale value. Run your own numbers with real bids.

What to watch out for

• Financing. FHA’s 203(k) rehab loan counts only 50% of the expected rent from a new ADU (HUD, October 2023). Rates are higher than a year ago, so get a rate quote before you commit.
• Fees. State law bars impact fees on ADUs of 750 sf or less. Larger units pay fees in proportion to the main house. Utility connection fees are separate.
• Short-term rental. Not allowed for JADUs and most ADUs under state law. Plan for 30-day-plus tenants.
• Owner occupancy. Not required for ADUs. Required only for a JADU that shares a bathroom with the main house (AB 1154, 2026).

How we use it

On larger lots, one rental unit is often not the best return. At the Foothill Residence, we stacked a 2-bed unit with a garage under the main home, so one lot carries two households. At Mariposa Complex in Altadena, we used SB 1123 to put three homes on one lot, each with an attached ground-floor ADU. If your lot qualifies, compare an ADU against a small-lot subdivision before you build.