House Hacking Calculator

House hacking means buying a multi-unit property, living in one unit, and renting the rest to offset — or even erase — your own housing cost, and this calculator is built around that offset math specifically. It first assembles your total monthly housing cost: the amortized mortgage payment, private mortgage insurance (automatically added whenever down payment is below 20%, at an estimated 0.5% annual rate on the loan balance), property taxes, insurance, maintenance, and any utilities you cover for tenants. Rental income from the units you rent out — reduced by a vacancy percentage — is then subtracted from that total to produce your net housing cost, and this is the number worth watching closely: when tenant rent covers more than your total cost, net housing cost goes negative, meaning tenants are not just covering your mortgage but paying you to live there.

The calculator also compares that net cost against a reference rent you supply (what you'd pay if you weren't house hacking) to show monthly and annual savings, and divides your net cost by the number of units you personally occupy to show cost per owner-unit when you occupy more than one unit. A key assumption to flag: FHA loans allow financing multi-family properties up to four units with as little as 3.5% down, but this calculator's default and PMI logic use a generic threshold rather than FHA-specific rules, so plug in your actual loan program's terms rather than relying on the defaults. It's also a first-year snapshot — it doesn't model rent increases, your eventual move-out, or renting the unit you currently occupy, all of which change the math substantially down the line.