The Rental Wire / Planning tools
House Hacking Calculator
Estimate your monthly housing cost while living in one unit of a duplex, triplex or fourplex. Compare it with renting every unit at the same property costs.
Live in one unit or rent every unit
Your own unit produces no rent while you live there. Every dollar of the whole-property cost budget is included in both columns.
| Monthly budget | Live in one unit | Every unit rented |
|---|---|---|
| Rent after vacancy | $1,710 | $3,610 |
| Management | −$137 | −$289 |
| Fixed property budget | −$3,100 | −$3,100 |
| Property cash flow | −$1,527 | $221 |
What if rents differ from your estimates?
Compare lower and higher rents while keeping the expense and reserve budgets fixed. This is a rent sensitivity check, not a growth forecast.
| Rent assumption | Your housing cost/mo | All-rented cash flow/mo |
|---|---|---|
| 10% lower | $1,684 | −$111 |
| Entered | $1,527 | $221 |
| 10% higher | $1,369 | $553 |
How house hacking reduces housing costs
Your housing cost = whole-property monthly budget − other-unit rent × (1 − vacancy rate) × (1 − management rate)
All-rented cash flow = rent from every unit × (1 − vacancy rate) × (1 − management rate) − whole-property monthly budget
A worked example
The example duplex costs $3,100 a month before percentage management fees, including the full mortgage payment, mortgage insurance, taxes, property insurance, utilities, maintenance and a replacement reserve. The other unit rents for $1,800. After 5% vacancy and 8% management, it contributes $1,573.20 toward costs, leaving you $1,526.80 a month to cover.
If your unit also rents for $2,000, combined rent after vacancy and management is $3,321.20. At the same $3,100 cost budget, the property has $221.20 monthly cash flow. That is property income before tax, not savings after paying for your next home.
Questions about house hacking
Can I use this for a triplex or fourplex?
Yes. Open Additional units and enter each extra unit’s scheduled rent. Unit 2, Unit 3 and Unit 4 are rented while you occupy your own unit. Enter whole-building costs once, not costs for only the rental portion.
Should I divide expenses between my unit and the tenants?
Not for this cash budget. You are responsible for the full property costs you enter, so the tool subtracts them in full. Expense allocation for taxes is a separate question and is not calculated here.
What if tenants cover more than the property costs?
The main result changes to a monthly surplus while you live here. It is the amount left after the entered costs and reserves. It does not mean the property has no costs or account for every personal expense.
Does the every-unit-rented case predict a later year?
No. It uses today’s entered rent, payment and cost assumptions. It does not add appreciation, rent growth, a refinance or mortgage-insurance cancellation. Revisit taxes, insurance, utilities and financing if your occupancy changes.
Can I enter rooms instead of units?
The arithmetic can represent separately rented rooms if you enter their actual rent and all shared costs. This page is structured around up to four units and does not assess whether a rental arrangement is permitted or eligible for financing.
Does this calculate investment return?
It estimates the monthly amount you need to cover while living here and property cash flow when every unit is rented. Purchase cash, appreciation, loan paydown and sale proceeds are outside this tool. Use the full calculator for a separate rental investment analysis.