The two-family maths that beats a 6.71% rate

At 6.71%, most buyers I meet have quietly decided they are priced out. Then we look at a two-family and the arithmetic changes completely. This issue is that arithmetic, on a house I actually have listed.

The same $750,000, two different monthly outcomes

Take 644 E 59th Street in East Flatbush — $750,000, three bedrooms, three baths, 1,332 square feet. Now compare buying it as a single-family against buying a comparable two-family where a tenant occupies the second unit.

Estimated monthly, 10% down at 6.71% over 30 years

Principal & interest on $675,000

≈ $4,360

the loan itself

Taxes, insurance, water — estimate

≈ $1,150

varies by block

Your payment, single-family

≈ $5,510

all of it yours

Second-unit rent, East Brooklyn 2BR

− $2,200

typical range

Your payment, two-family

≈ $3,310

40% lower

Illustrative. Principal and interest calculated at the Freddie Mac 6.71% average for 3 Sept 2026. Taxes, insurance and achievable rent vary materially by block and by unit condition — treat this as the shape of the maths, not a quote. Lender approval required.

The tenant is not paying your mortgage down. But at roughly $2,200 a month they are covering the difference between a payment you cannot make and one you can.

This is why two-family homes in Flatbush command a $880,000 median and see the strongest buyer competition in the area — about $165,000 above the single-family median a few blocks away in East Flatbush. Buyers are not paying extra for a building. They are paying for a lower monthly payment.

Four things to check before you fall in love with one

The certificate of occupancy. “Mother-daughter” and “used as a two-family for years” are not legal two-family. Your lender will underwrite against the C of O, not the current arrangement. I check this before showing you the house.

Whether the rent counts. Many loan programmes let you count a portion of projected rent toward qualifying income — often around 75% — which can be the difference between approval and denial. Ask your lender this specific question early, because the answer shapes your whole budget.

Who is already living there. An occupied unit comes with a tenancy, and in New York that means real obligations. Sometimes that is a feature: an in-place paying tenant is income from day one. Sometimes it is a problem. Either way you need to know before you sign.

Whether you actually want to be a landlord. This is the question people skip. Sharing a building means repairs at inconvenient hours and a working relationship with someone who lives downstairs. It is a genuinely good deal, and it is not for everyone.

$810k

Canarsie
single-family

$880k

Flatbush
two-family

+6.4%

East Flatbush
this year

With 3.8 months of supply, the well-kept two-families do not sit. If this is the route you are considering, the useful move is to get your lender’s answer on rental income now — before a house you want comes up.

Tell me your budget and I will find the maths that works →

I will run the real numbers on any house you send me, including one you found somewhere else.

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Lourdia Augustin

Licensed Real Estate Salesperson & Property Manager
Landmark Elite Homes by Dream Key Circle

347-414-3306 · dreamkeycircle@gmail.com

dreamkeycircle.com · Instagram · YouTube

Dream Key Circle · 2374 Grand Avenue, Baldwin, NY 11510
Serving Canarsie, East Flatbush, Flatbush, Flatlands, Mill Basin, Crown Heights, Brownsville & East New York.

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