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Buying a 2-4 Unit Building in SF as an Owner-Occupant

Updated 2026-10-25, 7 minute read

A two- to four-unit building is how many San Francisco buyers get a house-sized property they can finance: you live in one unit, tenants pay part of the mortgage, and the lender counts some of that rent. The catch: loan rules, the Rent Ordinance, insurance and taxes all change the moment a second unit is on the deed.

Why 2-4 units are the SF house hack

Single-family medians hit a record $2.15 million in March 2026 on Compass data, while condo medians ran roughly $1.1 million to $1.35 million in the first half of 2026 depending on the index (as of 2026-10-25, check current figures). No reliable SF 2-4 unit median is published, so measure what duplexes cost on your blocks with the comps tool.

What rent covers on a $1.6 million two-unit building, 20% down, at a 30-year rate of roughly 7.3% to 7.4%, where the Freddie Mac average sat in October 2026 (7.40% for the week of October 15; as of 2026-10-25, check the current figure):

Line	Monthly
Principal and interest on $1.28 million, plus property tax at the FY2025-26 rate of 1.1827%	about $10,350 to $10,440
Market rent, second unit (two-bedroom asking rents run roughly $4,000 to $4,800 depending on the index; as of 2026-10-25, check current figures)	$4,600, illustrative
Rent the lender counts after the vacancy haircut	about $3,450

Your share before insurance, maintenance and vacancy is roughly $5,750 to $7,000: rent softens the payment, it does not erase it.

Financing: unit count changes the rules

Conventional, 5% down. Since November 2023 Fannie Mae allows 5% down on an owner-occupied 2-4 unit purchase, down from 15% for two units and 25% for three and four, but high-balance and manually underwritten loans are excluded. So the loan must fit under the baseline conforming limit for that unit count ($832,750 for one unit in 2026, higher for more units); divide that baseline by 0.95 for the highest price at which 5% down works. Above it the older minimums return; above the high-cost ceiling you are a jumbo borrower, where 20% to 25% down and six to twelve months of reserves are typical. Even when conforming, Fannie Mae asks for six months of reserves on 2-4 units and prices in a multi-unit adjustment. Conforming vs jumbo in SF covers the tiers.

FHA, 3.5% down. FHA lends on owner-occupied one- to four-unit property with 3.5% down at a 580 score, within its county limits. On three and four units it adds a self-sufficiency test (75% of the appraiser's market rents must cover the whole payment) and requires three months of reserves. Many SF triplexes and fourplexes fail it.

How lenders count the rent

The appraiser prepares a rent schedule estimating market rent for each unit. Lenders generally use the lease rent for occupied units (many take the lower of lease and appraised rent), market rent for vacant ones, and a 25% vacancy and maintenance haircut, so 75% of the gross counts. A buyer with no history of receiving rental income and no current housing expense can, under Fannie Mae's rules, use the rent only to offset the building's own payment, not to add to income. The SF consequence: a long-term tenant paying $1,800 in a unit worth $4,600 counts as $1,350 after the haircut, and that rent can rise only 1.6% for March 2026 through February 2027 (confirm the current figure). Rent from a unit missing from the 3R report may not count at all; SF red flags covers pricing one.

Vacant or tenant-occupied: which unit can you live in?

Buildings with a certificate of occupancy before June 13, 1979 are under SF rent control, 2-4 units included: Costa-Hawkins exempts houses and condos, not duplex units, and SF has had no owner-occupied duplex exemption since Proposition I in 1994, even though the statewide rent cap does. Just cause has covered every unit since 2020, so in practice the ways into a tenant's unit are an owner move-in or a buyout.

An owner move-in needs at least a 25% ownership interest, intent to live there 36 continuous months, a Rent Board filing within 10 days of notice, and relocation payments that for notices served March 1, 2026 through February 28, 2027 run roughly $8,200 per tenant up to about $24,700 per unit, more for elderly, disabled or minor-child households (confirm current rates). Tenants 60 or older or disabled with 10 years of tenancy, or catastrophically ill with 5, are generally protected. Buyouts are regulated and filed with the Rent Board; compilations of those filings (most recently 2022 data) put the average payout around $35,000 per tenant, with a very wide range.

That is why "delivered vacant" is worth real money: you move in on recording and lease the other unit at market. Price an occupied building as though the tenants stay (buying a tenant-occupied home shows how), compare vacant and occupied sales in the comps tool, and have a landlord-tenant attorney review the leases before contingencies come off (when you need an attorney).

Retrofit and inspection exposure by building size

Soft story. Ordinance 66-13 mandated retrofits for pre-1978 wood-frame buildings with five or more units and three or more stories (or two over a basement). A 2-4 unit building with flats over an open garage is outside the mandate but can share the weakness; mandated seismic work can be passed through to tenants over 20 years, with hardship relief.
Meters and the lateral. Water and sewer often run through one SFPUC meter billed to the owner, and the entire sewer lateral belongs to the owner in SF; order a camera scope before offer day (inspectors and specialists).
Legal unit count. Only the 3R report tells you whether a "triplex" is legal; see the disclosure package.

Insurance on a building you partly rent

An HO-3 is written for an owner-occupied house; on 2-4 units most carriers write a dwelling or landlord form covering the structure, loss of rents when a covered loss empties a unit, and liability. The hard part in SF is getting written at all: knob-and-tube, an old roof or an unbolted foundation draws declines, some carriers skip older multi-unit buildings altogether, and the FAIR Plan fallback was reported to take an average increase of about 29% in October 2026 (check current figures). Earthquake is separate; confirm a CEA companion policy can attach to the building. Homeowners insurance and earthquake insurance have the process.

Taxes: two properties on one deed

The IRS treats your unit and the rentals as separate properties. Allocate the price between them, usually by square footage, split building from land, and depreciate the rental share over 27.5 years on Schedule E; the federal $750,000 acquisition-debt cap applies only to the loan share allocated to your unit. At sale, the $250,000 ($500,000 joint) exclusion covers only your unit's gain after two of five years of residence; the rental share's gain is taxable, depreciation is recaptured at up to 25% federally, and California taxes gain as ordinary income. The $7,000 homeowner exemption applies only to the part you live in. Tax benefits and the supplemental bill go deeper.

Exit paths, and valuing each

Exit	What it takes	What it is worth
Two-unit condo conversion	Both units owner-occupied by separate owners for a year; no disqualifying evictions	Closes the multi-unit and TIC discount; the lottery for larger buildings is suspended as of 2026-10-25; confirm with Public Works
Split into TICs	A TIC agreement; fractional loans about half a point to a point above condo rates	TICs trade below condos, commonly 10% to 20%
Hold as a rental	Just cause, 1.6% increases on covered units, landlord policy	Income plus appreciation; the exclusion lapses after three years away
Sell the whole building	Seller pays transfer tax by custom, 0.68% to 0.75%	Vacant buildings sell for more

The two-unit conversion is what makes a duplex special; buying with a friend or relative who takes the other unit is the usual route (TIC conversion and ADUs has the bars). Renting and selling after you buy covers the landlord years.

What to shop for right now

A lender who closes 2-4 unit loans weekly (savings: high): program fit, price adjustments and rent treatment differ sharply, and the gap between lenders is often approval versus denial. Landlord insurance through a broker and a direct carrier (savings: medium): pricing varies widely and some carriers decline older SF buildings. If you work with one of this site's agents, the buyer-side commission is how the site is paid; lender and insurance referrals never are.

Shop for this now

Service	When	Savings from shopping	How to shop it
Mortgage lender for 2-4 units	Before you tour, so you know whether 5% conventional, FHA, high-balance or jumbo fits the price band	High: shop it hard Freddie Mac's research puts the saving from multiple quotes at roughly $600 to $1,200 a year on typical loan sizes, and the spread is wider on multi-unit files because price adjustments and rent treatment are not standardized; on a 2-4 unit purchase the difference between lenders is often approval versus denial rather than a quarter point.	Request same-day quotes from a mortgage broker, a bank or credit union, and a portfolio lender, for the exact unit count and price. Ask each how it counts the rent schedule, whether it runs the FHA self-sufficiency test up front, what multi-unit and high-balance price adjustments apply, and how many 2-4 unit owner-occupied loans it closed in the past year.
Landlord or dwelling insurance	As soon as you are in contract, in parallel with the appraisal	Medium: worth 2-3 quotes Quotes for the same San Francisco building routinely differ by thousands of dollars a year, some carriers decline older multi-unit buildings outright, and the FAIR Plan fallback was reported to take an average increase of about 29% in October 2026 (check current figures), so two channels is the minimum; as of 2026-10-24 there is no reliable published SF landlord-policy benchmark.	Send identical inputs (year built, wiring, roof, foundation, unit count, the pest and inspection reports) to a direct carrier and an independent broker who writes older San Francisco multi-unit property, and ask for a landlord or dwelling form with loss of rents, liability limits that match an umbrella, and ordinance-or-law coverage.

Frequently asked questions

Can I buy a duplex in San Francisco with 5% down?

Sometimes. Since November 2023 Fannie Mae allows 5% down on an owner-occupied two- to four-unit purchase, but high-balance and manually underwritten loans are excluded, so the loan has to fit under the baseline conforming limit for that unit count, not the higher San Francisco ceiling. Divide the baseline limit for your unit count by 0.95 to get the highest price at which 5% down works; above that the older minimums of 15% for two units and 25% for three or four come back, and above the high-cost ceiling you are a jumbo borrower with the lender's own rules. FHA allows 3.5% down on one to four units within its county limits, with a self-sufficiency test on three- and four-unit buildings that many SF properties fail.

Does rental income count toward my mortgage on a 2-4 unit building?

Yes, partly. The appraiser prepares a rent schedule estimating market rent for each unit; lenders generally use the lease rent for occupied units (many take the lower of the lease rent and the appraised market rent), market rent for vacant units, and a 25% vacancy and maintenance haircut, so only 75% of the gross counts (confirm the factor with your lender). Fannie Mae also limits a buyer who has no history of receiving rental income and no current housing expense to using the rent to offset the building's own payment rather than to add to income. In San Francisco a long-term tenant far below market means the lender counts the low rent, not the market rent, which can sink qualification.

Can I move into one unit of a building I buy if it has tenants?

In practice only through an owner move-in eviction or a negotiated buyout, because every rental unit in San Francisco has just-cause protection. An owner move-in requires at least a 25% ownership interest, a genuine intent to live in the unit for at least 36 continuous months, a notice filed with the Rent Board within 10 days of service, and relocation payments that for notices served March 1, 2026 through February 28, 2027 run roughly $8,200 per tenant up to about $24,700 per unit, plus about $5,500 for each elderly, disabled or minor-child household member (confirm on the Rent Board's current rates page). Tenants who are 60 or older or disabled with 10 years of tenancy, or catastrophically ill with 5 years, are generally protected and cannot be moved out, and you get one owner's unit per building. If the plan depends on recovering a unit, have a landlord-tenant attorney review the file before you remove contingencies.

Is a 2-unit building in SF rent controlled?

If it received its certificate of occupancy before June 13, 1979, yes. The state Costa-Hawkins exemption from local rent limits covers single-family homes and condominiums, not units in a two- to four-unit building, and San Francisco's ordinance has had no exemption for an owner-occupied duplex since Proposition I in 1994, even though the statewide rent cap law does. Covered units can rise only by the Rent Board's annual allowable increase, announced as 1.6% for March 2026 through February 2027 (confirm the current figure), and you must register the building with the Rent Board's housing inventory before imposing any increase. Just-cause eviction rules apply to every unit in the city regardless of age.

Can I convert a two-unit building to condos in San Francisco?

It is the one conversion path still open without a lottery. A two-unit building can convert when both units are owner-occupied by separate owners who each hold the minimum ownership interest the Subdivision Code requires and have lived there as a principal residence for at least one year. Buildings with disqualifying eviction history, including an eviction of a protected tenant, cannot convert, and a unit legalized under the city's unwarranted-unit program cannot be subdivided. The annual lottery for larger buildings remains suspended as of 2026-10-25 (confirm the current status with Public Works), so a three- or four-unit building should be valued as though it will stay one parcel.

Do I pay capital gains on the rental units when I sell an owner-occupied duplex?

Yes. The IRS treats your unit and the rental units as separate properties. The federal exclusion of up to $250,000 of gain, or $500,000 on a joint return, applies only to the gain allocated to the unit you lived in for at least two of the five years before the sale. The rental share's gain is taxable at long-term capital gains rates, depreciation you claimed on it is recaptured at up to 25% federally, and California taxes the gain as ordinary income. Keep the allocation you used from year one so the split is defensible when you sell.