California mortgage answers · ADUs

ADUs and rental income: when the rent counts toward qualifying, and when it does not

An accessory dwelling unit changes two things on a file: the value of the property and the income the underwriter can count. Whether the rent counts depends on the loan program, the appraisal, whether the unit is permitted, and whether it is an existing unit or one you plan to build. The rules moved in 2026 and lender overlays sit on top of them, so an answer from a forum thread last year is often out of date.

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6 answers of 82 on the desk

What this topic is really about

The questions here are the ones owners and buyers ask in public: can the ADU rent help me qualify, does a permitted unit change the appraisal, what does an existing tenant do to the file, and how the loan already on a listing interacts with all of it. Each is answered against the current agency guide, with its source and its date.

On an ADU file the property question and the financing question are the same question. That is why the check at the bottom of every answer starts with the address.

By market

Every adus answer, by where the address is

Temecula, CA 1

ADU Property Value An ADU adds value two ways: appraised square footage, credited but not always dollar for dollar with construction cost, and rental or family-housing value, which never shows on an appraisal.

the San Gabriel Valley 1

Concerned about appraisal risk on ADU project in South El Monte An ADU build rarely fails on construction, it fails on appraisal because appraisers have fewer comparable ADU sales to draw from than they do for a main house.

Clairemont, San Diego 4

Breakdown of actual cost to build an ADU in San Diego One documented San Diego ADU build, plot plans and permits included, ran $327,756 total.
Got a bid for $185/sq ft for a detached ADU in Phoenix… A San Diego owner shopping ADU bids reported quotes running $275 to $350 a square foot locally, against a $185 a square foot bid seen out of Phoenix.
In San Diego, SDG&E has required a separate meter on new ADU construction since 2023. Owner and contractor forums describe SDG&E requiring a separate meter on new ADU construction since 2023, unlike some other utilities in the state.
How much cash do I need to build my ADU? An owner asking how much cash they need to build an ADU is usually sitting on the answer already, in the equity built up in the property itself.

On your file

What changes this answer on your file

Whether the unit is permitted and recorded, and whether the appraiser can find comparable rentals.
The loan program, since agency, FHA and portfolio lenders count the rent differently.
An existing lease against projected rent.
Whether the ADU is built, under construction or planned.
Lender overlays on top of the agency guide.

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Who answers

Nick Nagy

23 years in California lending · NMLS 314880 · CA DRE 01444600 · Loan Factory, Inc.

Dual licensed, so the loan side and the real estate side of a move are looked at as one problem instead of two. Most of what goes wrong in a move is a timing problem wearing a financing costume, and it is cheaper to catch it before you write an offer than after.

Financing is placed through Loan Factory, Inc. Real estate work is under CA DRE 01444600. More about Nick.

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The desk behind the file

One file, 237 lenders competing for it, and a broker who has done this for 23 years.

Loan Factory, Inc. is the brokerage. These are its published figures.

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A retail bank has one guideline book. When your file does not fit it, the answer is no and the reason is rarely explained. A broker shops the same file across the shelf and finds the lender whose box it already fits.

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Straight answers

Questions people here actually ask

The three most asked, in one sentence each. The full answers are on their own pages above.

ADU Property Value

An ADU adds value two ways: appraised square footage, credited but not always dollar for dollar with construction cost, and rental or family-housing value, which never shows on an appraisal. The full answer, with the local number and its source, is on its own page: https://go.homeaccesslist.com/answers/temecula/adu-property-value

Concerned about appraisal risk on ADU project in South El Monte

An ADU build rarely fails on construction, it fails on appraisal because appraisers have fewer comparable ADU sales to draw from than they do for a main house. The full answer, with the local number and its source, is on its own page: https://go.homeaccesslist.com/answers/sgv/adu-appraisal-risk

Breakdown of actual cost to build an ADU in San Diego

One documented San Diego ADU build, plot plans and permits included, ran $327,756 total. The full answer, with the local number and its source, is on its own page: https://go.homeaccesslist.com/answers/clairemont/adu-cost-breakdown-327756

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