Short-Term Rental Mortgage Seattle: Renting Part of Your Own Home

A short-term rental mortgage in Seattle starts with one fact: the loan on the home you live in was written for a home you live in. You can usually host guests in a room or an accessory unit without breaking that promise, as long as the house stays your principal residence. What hosting will not do on most loans is help you qualify, and an FHA loan on a home with an ADU forbids rentals shorter than 30 days outright.

This page is for owners and buyers in Capitol Hill, Wallingford and the rest of Seattle with a spare room, a basement unit or a backyard cottage, who want to know what renting it by the night does to their mortgage. My guide to a second home mortgage in Washington covers getaway properties outside the city. This one stays inside Seattle and inside the home you occupy.

For this page I read, on October 28, 2026, Fannie Mae Selling Guide sections B3-3.8-01 (general rental income), B3-3.8-02 (rental income from the subject property) and B3-3.8-03 (short-term rental), each dated 09/02/2026; the HUD 4000.1 handbook's restriction on hotel and transient use and form HUD-92561; the City of Seattle's short-term rental regulations page; and Washington's short-term rental chapter, RCW 64.37. The occupancy clause comes from the uniform Washington deed of trust (Form 3048), read for my seller rent-back guide. Freddie Mac's guide was not read for this page. Lenders can be stricter than any of these, and the answer for your file is confirmed per file.

The Occupancy Promise Behind a Short-Term Rental Mortgage in Seattle

The uniform Washington deed of trust, Fannie Mae and Freddie Mac Form 3048, has an occupancy section. In plain words, it says you will move in within 60 days of signing and live in the home as your principal residence for at least one year, unless the lender agrees otherwise in writing or circumstances beyond your control intervene.

That clause is about where you live. It does not mention guests. Renting a bedroom by the night while you sleep down the hall leaves the house your principal residence. So does renting a basement apartment or a backyard cottage on the same lot while you live in the main house. What changes the picture is moving out and listing the whole home during that first year, or buying with no plan to live there. That is an occupancy problem, not a hosting question, and stating an occupancy you do not intend to keep on a loan application is mortgage fraud.

The occupancy promise is the floor, not the whole answer. The loan program, the City and the condo association, if there is one, each add their own rules, and the rest of this page takes them one at a time.

Room, Basement Unit or ADU: Three Setups a Short-Term Rental Mortgage in Seattle Treats Differently

Seattle's short-term rental page draws the lines that matter, and they are not the lines most owners assume:

• A room in your home. Rooms without their own kitchen and bathroom are covered by the license for your primary residence. The City's own example: three rooms offered on a platform in the house you live in need one license, not three.
• A basement apartment or attached ADU. An accessory dwelling unit is a separate dwelling unit. It needs its own license to operate as a short-term rental, and because it is not your primary residence, the City says it must also be registered with the Rental Registration and Inspection Ordinance (RRIO) program.
• A detached ADU (DADU). The same treatment: a separate unit, its own license, RRIO registration.

The City also allows the reverse. Your primary unit may be the ADU or DADU itself, so an owner who lives in the backyard cottage and hosts in the main house has the main house as the second unit. Since January 21, 2026, most Seattle residential lots allow at least four homes, accessory units counted (see my guide to the Seattle zoning change), but the short-term rental cap below is per operator, not per lot.

Does Nightly Rent Count Toward a Short-Term Rental Mortgage in Seattle?

On a Fannie Mae conventional loan for the home you live in, no. Three sections of the Selling Guide, all dated 09/02/2026, line up:

• B3-3.8-01 says rental income from a borrower's one-unit principal residence generally cannot be used to qualify. The exceptions it names are boarder income and rent from an accessory unit.
• B3-3.8-03, the short-term rental section, applies to one-unit investment properties only. It requires the property to be legally permitted as a short-term rental, including local registration and licensing, and it says short-term rental income cannot be derived from an ADU.
• B3-3.8-02 allows rent from one existing ADU with a one-unit primary residence, on a purchase or limited cash-out refinance, capped at 30 percent of total qualifying income. That is rent under the long-term rules, documented the way my ADU rental income guide describes.

Put together: nightly rent from the ADU behind your house does not count, but a long-term lease on the same ADU may. Nightly guests in a spare bedroom are not boarders either. Fannie's standard boarder rule does not accept boarder income except in one narrow case, and its HomeReady exception requires a boarder who has lived with you for the last 12 months; my roommate income guide has the details.

The practical result for a short-term rental mortgage in Seattle: qualify on your own income, and treat hosting as money that helps you carry the payment, not money that helps you borrow more.

FHA and the 30-Day Rule on a Short-Term Rental Mortgage in Seattle

FHA is stricter, and the rule is written into the paperwork. HUD 4000.1 requires the lender to get the borrower's agreement that the property will not be used for hotel or transient purposes or rented for periods of less than 30 days, on form HUD-92561, for any FHA mortgage on:

• a one-unit home with an accessory dwelling unit;
• a two- to four-unit building; or
• a home that is one of five or more the borrower owns within two blocks.

The form quotes Section 513(a) of the National Housing Act: as long as the FHA insurance is in place, no portion of the housing covered by the mortgage may be used for transient or hotel purposes. HUD defines that as any rental for less than 30 days, or any rental with hotel services such as maid service or linens. The borrower promises not to rent, offer to rent or permit the offering of any part of the property on those terms. In short: if you bought a Seattle house with an ADU on an FHA loan, listing the ADU or a room by the night breaks a promise you signed. A 30-day-plus furnished rental is a different arrangement.

For a plain one-unit house with no ADU, the handbook does not list the form, but the statute is written about the housing the mortgage covers. Ask your lender before you list a room. VA rules were not read for this page; if you have a VA loan, ask the same question before hosting.

Seattle's Short-Term Rental License, Read at the Source

The City of Seattle's short-term rental page, run by Finance and Administrative Services, sets out the rules under Seattle Municipal Code 6.600 and the land use code at SMC 23.42.060. A short-term rental is a home or part of a home rented for fewer than 30 consecutive nights. To operate one you need:

• A Seattle business license tax certificate, and
• A short-term rental operator license, which costs $75 per unit and must be renewed every year. The license number has to appear on every listing in the format STR-OPLI-##-######, and platforms may remove listings that get it wrong.

The unit limit is what shapes most plans. Most operators may run two units: their primary residence and one unit they do not live in. The City defines an operator as a single person, a married couple, a group of people or an entity such as an LLC. The license has to be in the owner's name even when a management company runs the listing.

Other rules worth knowing before you buy with hosting in mind:

• Renters cannot get a license, apart from some Downtown Urban Core units operating before September 30, 2017.
• Some homes are excluded. The land use code bars short-term rentals in live-work units, caretaker's quarters, floating on-water residences (houseboats), waterfront residences and other areas where the Shoreline Code prohibits lodging, as well as RVs, tents, garages and boats. If you are buying on the water in Eastlake, my floating home financing guide covers the loan side.
• Penalties for operating without a license are $500 for the first violation and $1,000 for each one after.
• Your own home must meet basic habitability standards but does not register with RRIO. A dedicated unit, including an ADU on your lot, must register.

Washington's short-term rental chapter, RCW 64.37, adds statewide duties: give guests a contact for the length of the stay, comply with carbon monoxide alarm rules, and post the address, emergency numbers, a floor plan with exits, the occupancy limit and the operator's contact inside the unit. It also makes the operator responsible for lodging and sales taxes unless the platform collects them. Tax treatment belongs to your CPA and the Washington Department of Revenue; I do not cover it here.

The Insurance Gap Lenders Will Not Catch for You

Your lender requires hazard insurance on the home. It does not check whether that policy covers paying guests. Washington law flags the gap: RCW 64.37.040(5) requires platforms to tell every operator in writing that a personal policy on the home might not provide liability protection, defense costs or first-party coverage during short-term rental stays.

RCW 64.37.050 requires an operator to carry primary liability insurance of at least $1,000,000 for the unit, or to book every stay through a platform that provides equal or greater coverage. One nuance: the state chapter does not treat a home the owner occupies at least six months of the year, with fewer than three rooms rented at a time, as a short-term rental. The City's license rules still apply to that host, and the carrier's policy language still decides what is covered. Call your carrier before your first guest, and see my guide to homeowners insurance for a Seattle mortgage for what the lender itself requires.

Condos and HOAs: The Declaration Comes First

In a condo or a townhome with an association, the declaration and rules can bar short-term rentals regardless of the City or the loan. HUD 4000.1 lists a ban on leasing units for an initial term of less than 30 days among the provisions an FHA-approved project's documents may contain, and many Seattle associations have one. Read the rental section of the declaration and the resale certificate before you count on hosting; my condo resale certificate guide explains where to find it.

Heavy short-term rental activity in a building can also affect financing for everyone in it, because lenders review the project as a whole. A unit bought for nightly rental is an investment purchase, which is the next section.

When the Rental Is the Point: The Investor Path

If you are buying a place mainly to host guests, it is an investment property, and the loan should say so. Fannie Mae's B3-3.8-03 is the one place in its guide where nightly rent can count, and only on a one-unit investment property. On a purchase, the lender takes either a long-term market rent from the appraiser's Form 1007 or validated short-term data from three comparable rentals (average rate times average days rented), counts 50 percent of it, and subtracts the full payment with taxes, insurance and dues. A positive result can only offset that property's payment; a negative result counts as debt.

Remember the City cap: you may run one unit you do not live in, so a second investment rental in Seattle would have to be a 30-day-plus rental. Some investors use a DSCR loan, which qualifies on the property's rent rather than personal income. My guide to an investment property loan in Seattle covers the conventional side.

An Illustrative Short-Term Rental Mortgage Scenario in Wallingford

This example is illustrative only, written October 28, 2026. It uses no interest rate or income figure and does not describe a real borrower or property.

An owner in Wallingford bought a house with a basement apartment in 2025 with a conventional loan, lives upstairs, and wants to refinance and start hosting the basement unit by the night.

• Occupancy: the owner lives in the house, so hosting the basement does not change the principal residence.
• Qualifying: under Fannie Mae's B3-3.8-03, nightly rent from the basement ADU cannot be used. If the owner wants the unit's rent to count, it would need to be a long-term rental under B3-3.8-02, on a limited cash-out refinance, capped at 30 percent of qualifying income.
• City: the basement unit is a separate dwelling unit, so it needs its own operator license and RRIO registration, in addition to the license for the owner's home if rooms upstairs are also listed.
• Insurance: the owner calls the carrier and confirms whether the policy covers guests, or books only through a platform with qualifying liability coverage.

Had the same owner bought with an FHA loan, the signed HUD-92561 would rule out nightly rentals of any part of the house while the FHA insurance stays in place. The fix there would be a rental of 30 days or more, or a refinance out of FHA.

Before You List: A Short Checklist

• Pull your deed of trust and note the occupancy clause and its dates.
• Check your loan type. If it is FHA, find the HUD-92561 in your closing package.
• Confirm whether the space is a room or a separate dwelling unit under the City's definitions.
• Get the business license tax certificate, then the operator license for each unit.
• Register any dedicated unit with RRIO.
• Read the condo or HOA declaration's rental section.
• Talk to your insurance carrier and your CPA before the first booking.
• If you plan to buy or refinance soon, tell your lender about the hosting plan first.

FAQ: Short-Term Rental Mortgage Seattle Owners Ask About