A San Jose seller called her agent two weeks before a scheduled listing appointment with a simple question: does the "bonus unit" over the garage need to go on the flyer? The unit had a kitchenette, a full bath, and a tenant who had been paying $1,900 a month for three years. It also had no permit history anywhere in the county's building records. The buyer's inspector would find it in the first walkthrough, the appraiser would refuse to count its square footage, and the seller's lender disclosure obligations would apply whether or not the flyer mentioned it.
This is not a rare San Jose story. It is close to the median one.
The Incentive That Built the Problem
A Stanford and MIT research team used satellite imagery and computer vision to count detached accessory dwelling units built in San Jose between 2016 and 2020, then compared that count against the city's own permit records. The gap was enormous: 78 percent of the detached ADUs built in that window, roughly 1,045 units, had no permit on file. The researchers found these informal units clustered in denser, less affluent neighborhoods, and they pointed to a specific driver: San Jose's permit, plan review, and inspection fees for an ADU ran in the neighborhood of $3,000 to $4,700 at the time, a real barrier for a homeowner converting a garage into extra income or family space.
That fee gap is the mechanism worth sitting with. A few thousand dollars in permit costs, spread over years of rental income, looked like an easy number to skip. What that same homeowner was actually buying, without knowing it, was a liability that would surface at the one moment they have the least room to negotiate: escrow.
Three Places the Discount Shows Up
An unpermitted unit does not cost a seller once. It costs them three separate times, at three separate steps of the same transaction.
The appraisal is first. Appraisers work from the square footage on file with the local assessor and building department, not from what a homeowner built. Unpermitted additions can be noted in an appraisal report, but they typically contribute little or nothing to the appraised value, which means a buyer's loan amount is calculated as if the extra unit does not exist.
Financing is second. When the appraisal comes in under contract price because of unrecognized square footage, the buyer's loan-to-value ratio breaks. Someone has to bridge that gap: the buyer brings more cash, the price gets renegotiated, or the deal falls apart in the financing contingency window.
Disclosure is third, and it is the one that follows the seller after closing rather than stopping at it. California's Transfer Disclosure Statement law requires sellers of most one-to-four unit residential properties to disclose known unpermitted work, and that requirement cannot be waived even in an as-is sale. The standard is not whether the seller built the addition. It is whether the seller knew or reasonably should have known about it.
The thing that made an unpermitted unit profitable to build is the same thing that discounts it at the closing table. Cheap now, expensive later, and the bill comes due at the worst possible moment in the transaction.
The Window Just Widened
Sellers who bought a San Jose home within the last year and a half have one more layer to account for. California's Flipper Disclosure Law, which applies to offers accepted on or after July 1, 2024, requires a seller of a single-family residence who took title within 18 months of accepting an offer to disclose contractor-performed room additions, structural changes, and repairs, and to name the contractors involved. A seller who bought a house with an existing unpermitted garage conversion and then had contractor work done anywhere on the property inside that 18-month window is now pulling that history directly into the sale package, whether or not the garage conversion itself was their doing.
What the Three Paths Actually Cost
| Path | What it involves | Rough cost | Timeline |
|---|---|---|---|
| Sell as-is, fully disclosed | TDS discloses the unit's unpermitted status; price reflects the risk buyer is assuming | No legalization cost, but expect the appraisal and financing effects above to shape the offer | Can list immediately |
| Legalize before listing, using AB 2533 | Self-assessment, city inspection, corrections for health and safety items, final inspection | Typically five figures, often in the $15,000 to $50,000 range depending on what the inspector finds behind the walls | Several months from application to permit pass |
| Discovered mid-escrow | Buyer's inspector flags it after an accepted offer; seller scrambles to disclose, price, or fix under deadline pressure | Same corrective costs as above, plus a weaker negotiating position | Adds weeks to an already time-pressured escrow |
The math only looks close on paper. In practice, sellers who get ahead of it control the price conversation. Sellers who don't, don't.
What AB 2533 Actually Buys You
California's AB 2533, effective January 1, 2025, changed the legalization path for ADUs and JADUs built before January 1, 2020. Under this law, a city cannot deny a permit to legalize one of these units solely because it doesn't meet current building code or wasn't built with a permit in the first place. Impact and connection fees are waived unless new utility infrastructure is genuinely required to meet health and safety standards. And homeowners get up to five years to correct anything that isn't an immediate safety issue, rather than being required to bring the whole structure up to current code before the ink is dry on a permit.
San Jose runs its own ADU Amnesty Program built around these protections. A homeowner can start the process anonymously, using a self-assessment checklist and a confidential conversation with the city's Amnesty Coordinator, before any address is attached to the file. The city also waives the illegal construction penalty fee for every amnesty applicant, with additional fee relief available to homeowners who qualify for the Business Tax Financial Hardship Exemption. None of this requires a lawyer to access. It requires a phone call to the Amnesty Coordinator at 408-535-7770 or an email to [email protected], and a willingness to start before a buyer's inspector starts for you.
The Sequence If You're Listing This Year
- Pull the property's building permit history before you list, not after an inspection flags something. A Report of Residential Building Record can confirm whether a unit was ever permitted.
- If the unit is unpermitted and was built before January 1, 2020, call San Jose's Amnesty Coordinator and start the self-assessment checklist. You are not obligated to proceed just by asking.
- Get contractor quotes for any corrective work before you commit to legalizing, since concealed conditions behind finished walls are common in unpermitted construction and the final number can move once work starts.
- If you decide not to legalize before selling, price the listing with the appraisal and financing effects in mind, and disclose the unit's status clearly and early rather than letting a buyer's inspector be the one to raise it.
- If you've owned the property fewer than 18 months and had contractor work done anywhere on it, confirm what the Flipper Disclosure Law requires you to name on the disclosure package.
A Short FAQ
Does legalizing the unit erase my disclosure obligation? No. Once a unit is legally permitted, there's nothing unpermitted left to disclose, but the process of getting there, including any prior notices of violation, is still part of the property's known history until resolved.
What if the unpermitted unit was already there when I bought the house? The disclosure standard applies to what you know or reasonably should know as the current owner, regardless of who built the addition. Buying a house with an unpermitted unit does not exempt you from disclosing it when you sell.
Can I keep renting the unit while I go through the amnesty process? That depends on what the initial inspection finds. The self-assessment and eligibility conversation with the city's Amnesty Coordinator is the place to ask this before you're locked into a permit application.
Is there a deadline to use AB 2533? The law does not include a stated sunset date, but the amnesty applies specifically to ADUs and JADUs built before January 1, 2020. Waiting doesn't change eligibility, but it does mean living with the appraisal and financing friction longer than necessary.
If you're weighing whether to legalize before you list, price around the risk, or you're just trying to figure out what a garage conversion or backyard unit actually means for your sale, Megan DeVivo can walk through the specifics with you before the buyer's inspector does it for you. Let's Connect.
