Quick answer: A mother-in-law suite is a marketing term. Florida law uses "accessory dwelling unit" and defines it by its own kitchen, bathroom and sleeping area, but it does not require a city to allow one. Whether a suite in a Port St. Lucie home is permitted, rentable, or counted for an appraisal depends on the city's zoning, the building permit and the lender's rules. I could not confirm Port St. Lucie's current code from primary text, so get written zoning confirmation from the city before you rely on the suite.
Multigenerational living is a big reason buyers look for a second living space, and Port St. Lucie has many homes with a separate bedroom, bath and entrance. The trouble starts when a listing calls that space a "mother-in-law suite" and the buyer assumes it is a legal, permitted, rentable unit. Those are three separate questions. This guide explains how Florida law treats an accessory dwelling unit, what the city's code is still unclear on, and what lenders, appraisers and insurers may say about the space.
What Florida law says
Under Florida law, an accessory dwelling unit (ADU) is an ancillary or secondary living unit that has a separate kitchen, bathroom and sleeping area. It can be inside the same structure as the primary home or on the same lot (s. 163.31771(2)(a)). That definition is the test the statute uses, and it is narrower than many listings suggest. A room with a sink or a second microwave does not automatically meet it.
The statute is permissive. It says a local government "may adopt an ordinance to allow" ADUs in areas zoned for single-family residential use (s. 163.31771(3)). In other words, state law does not require Port St. Lucie or any other city to allow an ADU. Whether the city does, and under what conditions, is a local zoning question.
What the statute says about permits and affordability
The statute also says an ADU permit application must include an affidavit from the applicant attesting that the unit will be rented at an affordable rate to persons in extremely low, very low, low or moderate income categories (s. 163.31771(4)). The text applies to ADU permit applications generally. I have not verified whether Port St. Lucie applies this affidavit in practice, so ask the city's planning department directly if you are considering building or permitting an ADU.
What Port St. Lucie's code says, as far as I could confirm
I could not retrieve the city's zoning text, so I can't tell you the current answer from primary code. Two third-party zoning websites offer conflicting readings, and neither is the city code. One says ADUs are not a listed use in single-family districts and that unlisted accessory uses are prohibited under Sec. 158.217(C)(2). The other, citing a city planning FAQ, says the FAQ creates no blanket citywide ADU allowance and that the city limits lots to one principal building. Neither source settles the question for a specific parcel. Both point the same way for buyers: a suite should not be assumed permitted just because the home has one.
Lenders and the second kitchen
Fannie Mae's guidance on accessory units is useful for understanding what counts. An independent second kitchen by itself does not make an ADU. A unit that can only be reached through the primary dwelling is not considered an ADU for Fannie Mae's purposes, and the guidance allows one ADU per parcel. If local zoning prohibits an ADU, a loan may still be eligible if the lender confirms the conditions, according to its selling guide (B2-3-04, dated October 8, 2025). The lender decides, and the answer can change with the loan program.
Appraisal and marketability
The appraiser must describe an ADU and analyze any effect it has on value or marketability (Fannie Mae B4-1.3-05). Living area in an ADU is excluded from above-grade square footage unless it is inside the primary dwelling with interior access, and it appears on a separate line of the appraisal grid. Do not assume the suite adds value dollar for dollar. The appraiser's analysis of the local market decides that.
Renting the suite
Florida's vacation rental statute bars local governments from prohibiting vacation rentals or regulating how long or how often they are rented, except for ordinances adopted on or before June 1, 2011 (s. 509.032(7)(b)). That is a state-level rule about vacation rentals. It does not, by itself, tell you whether a particular suite may be rented, and I have not verified Port St. Lucie's own short-term rental rules. Any rental income also raises tax and landlord-liability questions that belong with a CPA and an attorney.
Permits for a new kitchen or bath
Under s. 553.79(1)(a), it is unlawful to construct, alter, modify, repair or demolish a building in Florida without first obtaining a permit. Adding a kitchen or bathroom is that kind of work. If the seller added a suite, ask for the permit records and any final inspection sign-off. An unpermitted addition can complicate the sale, the appraisal and an insurance claim.
Insurance
A secondary 2022 summary of homeowners insurance says a suite occupied by a relative in a single-family home is generally covered under the homeowners policy. Rent, separate utilities or a separate address can change that, and a two-family classification can require a separate policy. Ask your agent to confirm the answer in writing for the specific occupancy.
Advertising and fair housing
Describe the suite by its features, not by who should live in it. Florida's Fair Housing Act makes it unlawful to publish an advertisement that indicates a preference based on protected characteristics, including familial status (s. 760.23(3)), and the federal Fair Housing Act has a similar rule (42 U.S.C. 3604(c)). An ad that says "for relatives only" or describes a particular family type can cross that line. Rental or income claims must also be accurate.
What to do before you rely on a suite
Ask the seller for the permit history and any zoning letter. Ask the city for written zoning confirmation for the parcel. Ask your lender how it treats the unit. Ask your insurance agent how the suite is classified. Those four written answers will tell you more than the phrase "mother-in-law suite" ever will.
Questions buyers ask about in-law suites
Must Port St. Lucie allow a mother-in-law suite?
No. Section 163.31771(3) is permissive, so whether the city allows an accessory dwelling unit is a local zoning question. Ask the city for written confirmation for the specific parcel.
Is my in-law suite an accessory dwelling unit?
Possibly. Under s. 163.31771(2)(a), an ADU has a separate kitchen, bathroom and sleeping area. For Fannie Mae purposes, a second kitchen alone does not count, and a unit reachable only through the main home does not qualify as an ADU. Get the zoning answer in writing.
Can I rent the suite short-term?
State law bars local bans on vacation rentals and limits local rules on how long and how often they are rented (s. 509.032(7)(b)). I have not verified Port St. Lucie's own short-term rental rules, so check with the city before you list the suite.
Does an in-law suite affect the appraisal?
It can. The appraiser must describe the unit and analyze any effect it has on value or marketability. The suite is not automatically worth its construction cost, and the appraiser's market analysis controls.
Is the suite covered by homeowners insurance?
Generally, a relative-occupied suite in a single-family home is covered under the homeowners policy, according to a 2022 secondary summary. Rent, separate addresses or a two-family classification may change that. Ask your agent for a written answer.
Do I need a permit to add a kitchen or bathroom?
Yes. Under s. 553.79(1)(a), state law makes it unlawful to build or alter a building without first obtaining a permit. Confirm the city's permit process and final inspection requirements for the specific work.
Talk with William. Considering a Port St. Lucie home with a suite? Send me the listing. I will help you ask the seller for the permit history and the city for written zoning confirmation before you make an offer. Call or text (772) 800-2274 or send a message.
General information, not legal, zoning, lending, insurance, tax or financial advice. Zoning and permit rules are local and change; confirm them in writing with the City of Port St. Lucie. Rental income tax, landlord liability and loan eligibility belong with a CPA, an attorney or a lender. Statute references are as reviewed on October 20, 2026. William Merchant, REALTOR®, RE/MAX Gold. Each RE/MAX office is independently owned and operated. Equal Housing Opportunity.
Sources
- Florida Statutes 163.31771, Accessory dwelling units (2026)
- Florida Statutes 163.31771, Accessory dwelling units (2025 text, definition)
- Fannie Mae Selling Guide B2-3-04: Special property eligibility considerations
- Fannie Mae Selling Guide B4-1.3-05: Improvements, appraisal report
- Florida Statutes 509.032, Preemption of vacation rental regulation (2026)
- Florida Statutes 553.79, Permits (2025)
- RealTrends: In-law apartments and home insurance (C&S Insurance, Feb. 22, 2022, secondary)
- Florida Statutes 760.23, Discrimination in housing (2026)
- 42 U.S.C. 3604, Discrimination in the sale or rental of housing
- Fla. Admin. Code 61J2-10.025, Advertising rules for real estate licensees
