Tiny home vs ADU: cost, financing, resale and rent compared

This page compares the two on ownership and money. For the legal details of putting a tiny home in a backyard (permit paths, the city and county tiny-house rules, hookups), read our full guide to the tiny home ADU.

Tiny home vs ADU at a glance

Sources are linked in each section below.

Legal status

“Tiny home” isn't a legal category. The state's ADU handbook calls it an industry term and says a tiny home is subject to ADU law only if it meets the ADU definition. That definition requires complete independent living facilities, with permanent provisions for living, sleeping, eating, cooking and sanitation, on a lot with a home. HCD's tiny home bulletin treats most tiny homes on wheels as recreational vehicles or park trailers, which aren't intended for permanent occupancy unless a local ordinance allows it.

San Diego allows both. The City of San Diego's code permits one movable tiny house per lot in addition to any ADUs and junior ADUs, and defines it as 150 to 430 square feet. In unincorporated areas, the county's 2025 determination lets a permitted tiny home on wheels count as a dwelling, primary or accessory. The ADU route gets the state's rules: a decision within 60 days of a complete application and no impact fees on units of 750 square feet or less. Our summary of California ADU laws has the rest.

Cost and cost per square foot

A tiny home on wheels costs less in total because it skips the foundation and much of the permit work, but its published price is usually for the unit alone. Clever Tiny Homes, a builder, adds $1,000 to $25,000 for utility hookups and $2,000 to $10,000 for delivery. The ADU prices above are all-in, including design, permits and level-lot sitework in Snap ADU's case. Per square foot, small units of either kind cost more, because the kitchen, bathroom and hookups don't shrink with the floor area. See what an ADU costs in San Diego or try the ADU cost calculator.

Financing a tiny home vs an ADU

An ADU can ride on the house's financing. Fannie Mae's Selling Guide lists the construction types it accepts for an ADU: site-built, factory-built including modular, and HUD-code manufactured homes legally classified as real property and attached to a permanent foundation. A tiny home on wheels, which stays registered as a vehicle, isn't on that list. In practice, that means:

• ADU: home equity loans, HELOCs, cash-out refinances, construction loans and renovation mortgages are all used to build ADUs. Our guide to ADU financing compares them.
• Tiny home on wheels: you'll need cash or a loan outside your mortgage. Ask the seller and your lender what's available before you commit.

You can still use home equity to pay for a tiny home on wheels, but the loan is against the house, and the tiny home doesn't add to the collateral the way an ADU does.

Appraisal, resale and property tax

For appraisals, Fannie Mae's appraisal rules report an ADU on its own line, and treat a standalone structure that doesn't meet ADU requirements as an ancillary structure valued only for its contribution. A permitted ADU shows up as living space; a tiny home on wheels generally doesn't.

Resale works differently too. A tiny home on wheels can be sold on its own or towed to your next home. An ADU stays with the land, but in the City of San Diego, the municipal code allows an ADU to be sold separately as a condominium under state law. Our guide to ADU property value covers how much an ADU adds.

On taxes, the San Diego County Assessor adds only the value of new construction, like an ADU, to your assessment; the existing home isn't reassessed. A tiny home on wheels stays registered with the DMV under city and county rules. Ask the assessor how it will be taxed before you buy. More in ADU property tax.

Renting it out

Both can be rented long term in the City of San Diego, but not as short-term vacation rentals. The city's code requires ADU rentals of at least 31 days and movable tiny house rentals of at least 30 days. Rules for vacation rentals are in our guide to ADU short-term rental rules.

An ADU is a full home built to the same building code as the house, and in the city it can be up to 1,200 sq ft new. A tiny home on wheels in the city is limited to one story, 430 square feet and no gas connection, which limits who it suits as a long-term rental. For rent figures, see ADU rental income in San Diego.

Which one fits you

Either way, someone licensed should do the site work. The Contractors State License Board says a B contractor can build or install ADUs, and state law caps the deposit on a home improvement contract at $1,000 or 10%, whichever is less. Check a contractor's license and read how to hire an ADU contractor. Comparing factory-built ADUs? See prefab ADUs in California and our neutral list of prefab ADU companies. For a site-built unit, compare verified ADU builders in San Diego or start with the best ADU builders in San Diego. Converting a garage instead? Our garage conversion ADU guide and garage conversion cost breakdown cover the cheapest ADU route for many lots.

Common questions