How we grade
How a house earns its grade.
Every multi-family listing in Suffolk County takes the same exam. Most fail. This page is the whole exam — no black box, no vibes.
The one question
What would it actually cost you, net, to live there?
We price every property the way a first-time house-hacker would buy it: an FHA loan at 3.5% down, today's published rate (6.33% as of Aug 26, 2026), real listed taxes, and Long Island insurance. You live in the smallest unit; the others rent at what places that size actually leased for nearby — the median of real closed OneKey leases, not a published schedule — counted as rented year round. What's left after tenant rent is your check each month. Then we subtract the year-one principal you pay down — that money isn't spent, it's moved into equity you own. The result is your net cost to live there, and the grade is that number measured against what renting your own unit would cost on the open market.
The ladder
Living there costs almost nothing, net. The tenants and the equity you build carry nearly the whole load. Rare — when one appears, it goes fast.
Your net cost is less than half what renting the same-size unit would run. These are the properties the board exists to catch.
A clear, strong win over renting — net cost at 40% off market rent or better.
A solid hack. Roughly a third off what renting your unit would cost, and you own the building.
The board's floor. A real discount to renting — at least 15% off, net — plus everything ownership does for you that rent never will.
Below B doesn't make the board. And grades move in either direction — a price cut can promote a listing onto the board, a rate move can demote one off it. That's the point of editions.
What moves a grade
Up
- Separate electric meters — tenants pay their own utilities.
- Clearing FHA's self-sufficiency test on 3–4 unit buildings.
Down
- Priced over the FHA loan limit for its unit count.
- Failing the self-sufficiency test (3–4 units).
- Property taxes running heavy against the price.
Seasonal communities, land leases, co-ops, and age-restricted buildings are disqualified outright — they can't be hacked the way this board means it.
The FHA math, honestly
FHA lets you buy a 2–4 family home with 3.5% down as long as you live in one unit. The 2026 loan limits for Suffolk County: $1,249,125 for one unit, $1,599,375 for two, $1,933,200 for three, $2,402,625 for four. Two costs come with it: an upfront mortgage insurance premium of 1.75% (we fold it into the loan, like your lender will) and annual mortgage insurance of 0.75% — both are in every worksheet on this site. When you qualify, lenders can count 75% of the market rent from the other units as your income. And on 3–4 unit buildings, FHA's self-sufficiency test requires 75% of all units' market rent to cover the full monthly payment — a test many Long Island triplexes fail, which is why we show it on the card instead of letting you find out in underwriting.
The Quiet Files — how we find hidden apartments
Most Long Island house-hacks aren't listed as two-families. They're single-family homes with a second kitchen — the classic mother/daughter — and because many of those kitchens were never permitted, listings rarely say it plainly. So we read every single-family listing in Suffolk County three ways: the listing's own language (mother/daughter, in-law, proper permits, second kitchen — including the coded phrasings), the structured MLS record (accessory-apartment and in-law-floorplan flags agents file but buyers never see), and the listing photos themselves, reviewed for a second kitchen. Each find lands on one of three shelves: On the record (the listing cites permits), In plain sight (a second kitchen stated or visible), and Between the lines (the language and layout point to an apartment).
Why it works with FHA: appraisers in this market generally treat a second kitchen as normal and customary for the area, so these homes finance as ordinary single-families — 3.5% down against the one-unit limit of $1,249,125, no self-sufficiency test. The worksheet math assumes the accessory space rents as a one-bedroom at the local median. Whether it lawfully can is a town question — a second kitchen is not a legal apartment, permits are property- and often owner-specific, and we verify with the town before you offer. Your lender and appraiser make the final call on any property.
Where the numbers come from
Listings, prices, taxes
OneKey MLS, refreshed daily
Rents
Median of 7,109 closed Suffolk leases on OneKey since 2025-01-01 — by town where we have 5+ of them, county median otherwise: $2,405 (1 BR) · $3,100 (2 BR) · $3,800 (3 BR)
Rates
6.33% FHA / 6.75% conventional, published averages as of Aug 26, 2026
FHA limits & rules
HUD, 2026 Suffolk County
Insurance
Long Island multi-family carrier averages
The town matters
Suffolk County is ten towns with ten rulebooks on rentals, permits, and accessory apartments. The grade doesn't bake this in — it's a conversation your agent has with you per property, and permits are verified before any offer. The short version:
Babylon
Legal two-family homes exist in the code, but a rented unit in a non-owner-occupied home requires a Town rental permit. Verify the C of O actually says two-family.
Huntington
Rental permits are required with an engineer/architect or code-official certification — a legal two-family needs a valid C of O plus a current rental permit before the second unit is rented.
Smithtown
Legal two-family homes are rare here. Rentals must be registered, and a registered rental must be leased in its entirety as one dwelling — no partitioning into apartments.
Islip
A true legal two-family (C of O as two-family) is the clean play; any rented unit in a non-owner-occupied home needs a Rental Occupancy Permit, and advertising without one is itself a violation.
Brookhaven
Existing legal two-families need a rental license through the Building Division for rented units, backed by a valid C of O and an inspection.
Riverhead
Rental dwellings, two-family included, need an annual Town rental permit with safety inspections (interconnected smoke detectors; extra requirements for 3+ units).
Southampton
Very little legal 2-4 family stock; any rental occupancy requires a Chapter 270 rental permit with inspection, and rentals under 14 nights are prohibited — units must be long-term leases.
Southold
All residential rentals require an annual rental permit backed by a valid C of O — an un-certificated second unit cannot be legally rented.
East Hampton
Two-family houses fall under the town Rental Registry; legal 2-4 family stock is minimal and pricing rarely pencils for FHA house-hacking.
Every number on this site is a financing cost estimate built from published data — not a valuation, an appraisal, or an opinion of any property's worth, and not a promise of what any unit will rent for. Rents are the median of closed leases nearby, not a quote for a specific apartment. Rates move daily; your lender's quote governs. Listed taxes come from the MLS and are verified in diligence.
Grades measure one thing only: the estimated cost of financing and offsetting a property at its asking price under one standardized scenario. They say nothing about condition, neighborhood, schools, or who should live where — pick the areas that fit your life, and we'll run the numbers there.
FHA program rules summarized here are simplified. Whether you qualify — and on what terms — is your lender's determination, not ours.