Effective housing cost: the one number house hackers should track

Effective housing cost is defined as your total monthly housing payment minus the rent you collect from the other units. It measures what you personally pay to live in the property, not what the property cash flows. On my duplex the payment is about $3,100 and the two units bring in roughly $2,200, so my effective housing cost is about $900/month while I build equity.

Forget “cash flow” for a second. This is the number that actually changed my life.

Most real estate content trains you to obsess over cash flow, does the property make money each month? For a house hacker, that’s the wrong first question, and chasing it will talk you out of good deals.

The number that matters is your effective housing cost: what you actually pay to live there each month after your tenants chip in.

Effective housing cost formula

It’s almost embarrassingly simple:

Effective housing cost = your total monthly housing payment − rent collected from the other units.

That’s it. Your mortgage, tax, insurance, and mortgage insurance, minus what your tenants pay you.

Effective housing cost example on my duplex

My total monthly housing payment (PITI) on the duplex is about $3,100. While I live here:

• Upstairs tenant pays about $1,200
• Basement short-term rental averages roughly $1,000

So roughly $3,100 − $2,200 = an effective housing cost of about $900/month.

Before the duplex, I was paying $1,500/month to house myself. The house hack cut that by roughly 40%, and it did it while I built equity on a $470,000 asset.

Why this beats “cash flow”

If you only looked at my property’s cash flow, you’d see a loss, because I live in one unit rent-free, a third of the building produces no income. On paper the property “loses” money. In reality, I win by hundreds of dollars a month. The arbitrage doesn’t show up on the property’s books. It shows up on mine.

That’s why effective housing cost is the house hacker’s true scoreboard. Cash flow is for pure rentals. Effective housing cost is for people living in the deal.

What counts as “good”

There’s no universal number, but a useful test: compare your effective housing cost to what you’d pay to rent a comparable place. If you’re housing yourself for meaningfully less and building equity, the deal works, even if the property’s cash flow line looks ugly.

A bonus that is easy to forget: the day you move out, every unit rents, and the property’s standalone math usually flips positive. You were never really losing money. You were buying a discount on your own rent and an asset at the same time.

The number that matters is your effective housing cost: what you actually pay to live there each month after your tenants chip in.

Free effective housing cost calculator

The calculator computes this directly, plug in a real listing and the expected rents, and it’ll show your effective housing cost in seconds. That single number tells you more about a house hack than any cash-flow figure ever will.

Tracking a listing right now? I’ll run the numbers with you.

Frequently asked questions

What is effective housing cost

Effective housing cost is defined as your total monthly housing payment minus the rent you collect from the other units. It measures what you personally pay to live in the building, not what the building earns as an investment.

How do you calculate effective housing cost

The formula is defined as total monthly payment minus rent collected from the other units. On the duplex in this post that is roughly $3,100 minus $2,200, which leaves an effective housing cost of about $900 a month.

Why is cash flow the wrong number for a house hack

Cash flow is defined as what a property earns after every expense, counting the unit you live in as producing no rent. On a house hack that line can read as a loss while you are personally hundreds of dollars a month better off, which is why effective housing cost is the better scoreboard.

What is a good effective housing cost

A good result is defined by comparison rather than by a fixed number. Put your effective housing cost against what renting a comparable place in the same area would cost you, and if you house yourself for meaningfully less while building equity, the deal works.