Real Estate Tax Calc
The standard formula still applies
Cash-on-cash return = annual pre-tax cash flow / total cash invested. For a house hack, the challenge is defining 'cash flow' when you also live in the property. One approach: treat the entire property as a pure rental (both units at market rent) to get the unleveraged investment return. A second approach: measure your actual out-of-pocket cost after rental income and compare it to what you would otherwise pay in rent.
A worked example
You buy a duplex for $400,000 with 10% down ($40,000) plus $6,000 closing costs = $46,000 total invested. You live in one unit; the other rents for $1,800/month. Your total PITI (principal, interest, taxes, insurance) is $2,400/month. Net out-of-pocket: $2,400 - $1,800 = $600/month, or $7,200/year. Your personal housing cost is just $600/month instead of market rent (say, $1,400/month for a comparable unit). The implicit housing savings of $800/month = $9,600/year can be thought of as return on your $46,000 investment — roughly 21% annually, before equity buildup.
Modeling the full investment return
For a cleaner comparison to other investments, model both units as rentals: $1,800 x 2 = $3,600/month gross, minus all expenses and debt service. That gives the property's pure cash-on-cash return. Then add back the housing benefit. Most investors find house hacking produces substantially higher effective returns than either pure investing or pure renting in the same market — it is why the strategy is often recommended for first-time investors.
Two definitions, one deal — worked both ways
Return to the duplex: $400,000 price, $46,000 all-in cash invested, you live in one unit, the other rents for $1,800, and total PITI is $2,400/month. Definition one — housing-cost method: your out-of-pocket housing cost is $2,400 - $1,800 = $600/month. Compared with the $1,400/month you would pay to rent a similar unit, you save $800/month, or $9,600/year. Against $46,000 invested, that housing benefit alone is about a 21% return — before appreciation or loan paydown.
Definition two — pure-rental method: pretend you do not live there. Both units rent for $1,800 = $3,600/month gross. Subtract vacancy, taxes, insurance, maintenance, and the $2,400 debt service and you might net, say, $300/month, or $3,600/year — roughly an 8% cash-on-cash return as a straight investment. Neither number is wrong; they answer different questions. Use the housing-cost method to decide whether to house hack versus rent, and the pure-rental method to compare the property against other investments.
How a house hack is taxed
The tax treatment follows the split between your personal space and the rented space. You allocate shared costs — mortgage interest, property tax, insurance, utilities you pay, and depreciation — between the two, usually by square footage or by number of units. The rental portion goes on Schedule E: you deduct that share of interest, taxes, insurance, repairs, and depreciation against the rent you collect.
The personal portion is treated like any homeowner's: your share of mortgage interest and property tax is deductible on Schedule A only if you itemize. Splitting a duplex 50/50 is straightforward; a rented spare bedroom is typically allocated by the fraction of the home's square footage that is exclusively the tenant's plus a share of common areas. Keep the allocation reasonable and documented.
Depreciation on the rental portion
You can depreciate the rental portion of the building (never the land, and never your own living space) over 27.5 years. If the building's depreciable basis is $320,000 and you rent half, you depreciate $160,000 — about $5,818 a year — as a non-cash deduction that often shelters much of the rental income.
Two consequences follow. First, that depreciation reduces your basis in the rented portion and is subject to recapture when you sell, at up to 25%. Second, if you later move out and rent the entire property, the portion that was your residence converts to a rental at that point, and its depreciable basis is generally the lesser of adjusted basis or fair market value at the date of conversion. Track the allocation carefully so the numbers are defensible years later.
Low-down-payment financing supercharges the return
The reason house hacking produces such high cash-on-cash returns is owner-occupant financing. Because you live in the property, you qualify for loans unavailable to pure investors: FHA loans as low as 3.5% down, conventional owner-occupied loans around 5%, and VA loans at 0% down for eligible veterans. On a $400,000 duplex, 3.5% down is just $14,000 instead of the 20-25% ($80,000-$100,000) an investor would face.
A smaller cash outlay in the denominator of the cash-on-cash formula mechanically lifts the return — and it lets first-time investors start with far less capital. Most owner-occupant loan programs require you to live in the property for at least 12 months, so plan to occupy it for at least a year before converting or moving on.
Exit, conversion, and the Section 121 angle
House hacks create a useful exit option. If you live in the property as your primary residence for at least two of the five years before selling, you may exclude gain under Section 121 — up to $250,000 single or $500,000 married — but only on the portion attributable to your residence use, not the rented portion. Gain allocable to the rental unit is taxed, and depreciation you claimed (after May 6, 1997) is recaptured regardless of the exclusion.
A popular sequence is to house hack for a year or two, move out, rent the whole property, and either hold it as a full rental or sell within the Section 121 window to capture the exclusion on your former unit. Each path has different tax consequences, so model the sale before you move rather than after.
Common house-hack math mistakes
First, double-counting the benefit — do not add both your housing savings and the full rental cash flow as if they were separate; pick one framework and apply it consistently. Second, ignoring the reserves you still need — living in the building does not exempt it from vacancy, turnover, and CapEx, and a roof or furnace does not care that you sleep upstairs.
Third, forgetting the plan after year one — a house hack that looks brilliant while you occupy it may be only an average rental once you move out and rent your unit at market too. Run the numbers for both the occupied period and the fully-rented period so you know what you actually own once you leave.
Beyond the duplex
Duplexes and small multifamily are the classic house hack, but the same math applies more broadly. Renting spare bedrooms in a single-family home, adding and renting an accessory dwelling unit (ADU) or basement apartment, or renting a portion as a short-term rental all offset your housing cost and can be modeled the same two ways.
The trade-offs differ: rooms mean sharing your living space, an ADU requires capital and permits, and short-term rentals bring higher income but more work and different tax rules. Whichever form you choose, the core idea is identical — let the property pay part of your housing cost, shrink your effective invested capital, and let the cash-on-cash return climb accordingly.
Counting the return honestly across the hold
A house hack's return changes over time, so measure it in phases. During your owner-occupied phase, the housing-cost method captures the real benefit — the rent you collect plus the market rent you avoid paying, against your small down payment. This is usually where the eye-popping returns come from, precisely because your invested capital is tiny under owner-occupant financing.
After you move out and rent your unit too, switch to a straight rental cash-on-cash calculation on the whole property. Add the loan paydown your tenants are funding and any appreciation, and you have a total-return view for the second phase. Investors who model only the glamorous occupied-phase number are often surprised when the fully-rented property settles into an ordinary — though still solid — return. Run both phases so the decision to buy, hold, or sell rests on the complete picture rather than the best-looking year.
Frequently asked questions
How do I calculate cash-on-cash on a house hack?
Divide annual net cash flow (rent received minus out-of-pocket housing expense) by total cash invested. Or model it as a pure rental to see the unleveraged return.
Is a house hack a good investment?
Often yes — offset housing costs plus equity building make it one of the highest-return strategies for beginning investors, especially in expensive markets.
How is a house hack taxed?
You allocate shared costs between your personal space and the rented space, usually by square footage or units. The rental share of interest, taxes, insurance, repairs, and depreciation goes on Schedule E; your personal share of interest and property tax is an itemized deduction on Schedule A.
Can I claim depreciation on a house hack?
Yes, on the rental portion of the building (not your living space and not the land), over 27.5 years. That depreciation is subject to recapture at up to 25% when you sell.
Does house hacking work with a single-family home?
Yes — renting spare bedrooms, adding an ADU or basement apartment, or renting part of the home short-term all offset your housing cost and can be modeled the same way as a duplex.
What financing can house hackers use?
Because you occupy the property, you qualify for owner-occupant loans: FHA around 3.5% down, conventional near 5%, or VA at 0% for eligible veterans. Most require you to live there at least 12 months.
Which method should I use to measure a house hack's return?
Use the housing-cost method (rent collected plus market rent avoided, over your down payment) to decide whether to house hack versus rent, and the pure-rental cash-on-cash method to compare the property against other investments. Model both the occupied phase and the fully-rented phase so you see the return across the whole hold, not just the best-looking year.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.