Using ADU Rental Income to Qualify for a Mortgage in California 2026

I’m Michael DiVita — DRE #01372066 | NMLS #241655, DiVita Home Finance (DRE #01818285 | NMLS #323700), Tiburon, CA. I’ve been in California mortgage lending since 2000 and founded DiVita Home Finance in 2007. Call (800) 239-1103.

California leads the nation in ADU (Accessory Dwelling Unit) construction — backyard cottages, garage conversions, basement apartments, and junior ADUs attached to the main home. Millions of California properties now have one, and millions more are being built every year thanks to state legislation that dramatically simplified permitting. If you’re buying a home with an existing ADU or planning to add one, that rental income can meaningfully increase how much mortgage you qualify for — but the rules are specific and many loan officers apply them incorrectly.

Fannie Mae’s ADU Income Rules

Fannie Mae updated its ADU guidelines in 2023 to be more permissive, recognizing California’s ADU boom. Current rules allow rental income from an ADU to be used in qualifying under the following conditions:

The 75% haircut is standard — Fannie Mae applies it to account for vacancy and maintenance. If the ADU rents for $2,000/month, $1,500/month ($2,000 × 75%) is added to your qualifying income. On a purchase at current rates, $1,500/month in additional income can increase your qualifying loan amount by approximately $200,000–$250,000.

What “Legally Permitted” Means — and Why It Matters

The ADU must be a legal, permitted structure to count its income. An unpermitted garage conversion — even if someone has been renting it for years — cannot be counted in the qualifying income calculation and may create appraisal problems. Before relying on ADU income in your mortgage qualification, confirm the ADU has: a permit from the local building department, a certificate of occupancy (or equivalent final inspection sign-off), and clear designation on the property records as an ADU or second unit. Unpermitted ADUs are common in California — agents and sellers don’t always disclose this. Pull the property’s permit history before assuming the ADU income is usable.

ADU Income and FHA / VA Loans

FHA allows ADU rental income to be counted when the buyer will occupy the main unit, the ADU is a legally permitted separate unit, and income is documented with a lease or market rent estimate from the appraisal. VA loans permit ADU rental income on a case-by-case basis through VA lender overlays — not all VA lenders count it, and the rules are less standardized than Fannie Mae’s. If ADU income is essential to your VA loan qualification, confirm with your lender upfront that they accept it.

Building an ADU: Can You Finance It?

If you own a California home and want to add an ADU, financing options include: cash-out refinance (access equity to fund construction), home equity line of credit (HELOC), construction loan (specialized product — DiVita originates these), and Fannie Mae’s HomeStyle renovation loan (purchase + renovation cost combined into one loan). Once the ADU is built and permitted, a refinance using the ADU’s rental income can often improve your rate and payment by increasing your qualifying income.

See our full ADU Income Mortgage California guide for all loan options and strategies.

If you’re planning to build an ADU from scratch on a vacant lot or alongside a new primary residence, see our full guide to construction loans in California for build-phase financing options.