The Real House Hacking Math on a Twin Cities Duplex
Most "house hacking" advice skips the one thing you actually need: the math.
People love to tell you the concept. Buy a duplex, rent the other side, let the tenant pay your mortgage. Great. But when you ask what your number actually is at the end of the month, the conversation gets vague. So let's not be vague. Let's run it.
Quick note before we start: every number below is an illustration to show you how the pieces fit, not a quote and not a financing offer. Your real figures depend on the building, the rate you lock, and the rents — so treat this as a framework, then plug in a real property.
Start with the payment
Say you buy a Twin Cities duplex for $375,000 and use an FHA loan with 3.5% down. That's about $13,125 down, leaving roughly $361,875 financed.
Your monthly payment isn't just principal and interest. It's PITI — principal, interest, taxes, and insurance — plus mortgage insurance because you put less than 20% down. At a rate near where the market sat in mid-June 2026 (the 30-year fixed averaged 6.52%), your principal and interest alone runs in the low-$2,000s per month. Add property taxes, homeowner's insurance, and FHA mortgage insurance, and your all-in payment lands somewhere around $2,800 to $3,000 for the whole building.
Hold that number. That's what the building costs you each month before any rent.
Now bring in the tenant
You're living in one unit and renting the other. What does the other unit bring in?
Across Minneapolis, average rents in 2026 ran roughly $1,500 to $1,700 for a typical apartment, depending on the source and the neighborhood, with two-bedroom units higher. For this illustration, let's be conservative and say the rentable unit brings in $1,400 a month.
That $1,400 comes straight off your payment.
What you actually pay to live
Here's the whole thing in one place:
Total building payment (PITI + mortgage insurance): roughly $2,900
Minus rent from the other unit: $1,400
Your out-of-pocket cost to live: about $1,500 a month
Now compare that to renting. If you were going to rent a comparable place in the metro anyway for $1,500 or so, you're now paying about the same — except a chunk of that payment is going to principal, which is your equity, not your landlord's. That rental income offsets your mortgage and lowers your living expenses, and the part you do pay is building something you own.
That's the reframe. You didn't find a way to live for free. You found a way to make the money you were already spending on rent start working for you.
The math that makes people uncomfortable
I'm not going to hide the rough edges, because they're real.
Vacancy happens. If your tenant moves out, you're covering the full $2,900 until you fill it. You need reserves for that — don't buy right up to the edge of your budget.
Repairs happen. The furnace, the roof, the water heater. As the owner, that's you now. Set money aside every month like it's a bill, because eventually it is one.
Mortgage insurance is real cost. At 3.5% down on an FHA loan, you'll carry it until you build equity — though, as I've written elsewhere, you can work to remove it down the line.
And rents aren't guaranteed. The $1,400 is an estimate. Pull actual comparable rents on the specific building before you ever write an offer. The deal lives or dies on real numbers, not optimistic ones.
Why I run it this way
At the end of the day, house hacking math is just honest subtraction. Payment minus rent equals your number. The mistake people make is using a hopeful rent and forgetting vacancy and repairs. Do it conservatively and the strategy still works — that's how you know it's a good deal instead of a good story.
I built a guide that walks through this math step by step, with the loan options and a worksheet you can run on a real property. Send me an email, and I'll send you the house hacking guide.