House Hacking Calculator

House hacking means buying a small multifamily property (2-4 units), living in one unit, and letting the rent from the others cover most — sometimes all — of your mortgage. Because you occupy the property, you qualify for owner-occupant financing: as little as 3.5-5% down instead of the 20-25% an investor would need.

This house hacking calculator compares your effective monthly housing cost as a house hacker against what you're paying today, and separately shows the property's cash flow once you eventually move out and rent every unit at market.

$420,000 duplex, 5% down, 6.9% rate over 30 years, $180/mo mortgage insurance, $8,800 annual property tax, $2,600 annual insurance, 5% maintenance reserve, $1,450/unit rent, 5% vacancy, $1,600 current rent:

• Loan amount: $399,000 | Down payment: $21,000
• Monthly P&I: $2,627.81 → Full PITI + MI: $3,757.81
• Tenant income (other unit, after vacancy): $1,377.50
• Effective housing cost: $2,525.31 — versus your current $1,600 rent, that's roughly $925/month more while you occupy the property
• Once you move out and rent both units at market: cash flow is -$1,147.81/month at these assumptions — this deal needs higher rent or a smaller loan to cash flow post-move-out

This example deliberately shows a deal that costs more than renting and doesn't cash flow after move-out, because that's the realistic outcome in many high-price markets — the calculator's job is to show you that clearly before you make an offer, not to talk you into a deal. Raising rent to $1,750/unit or dropping the purchase price to $360,000 flips both numbers positive; try your own local rents and prices to see where the line sits for you.

The math has three layers:

1. Full housing payment — principal, interest, taxes, insurance, and mortgage insurance (if your down payment is under 20%), plus a maintenance reserve as a percentage of total rent across all units.
2. Effective housing cost while you live there — the full payment above, minus the rent from the unit(s) you don't occupy (after a vacancy discount).
3. Post-move-out cash flow — once you eventually move out and rent your own unit too, all units' rent (after vacancy) minus the full payment.

FHA loans allow 3.5% down on 1-4 unit owner-occupied properties, and conventional owner-occupant programs typically start around 5%. Below 20% down you'll generally carry mortgage insurance, which the calculator includes as its own line item.