Your Mortgage Payment Is Mostly Interest, and Interest Doesn’t Come Back Either
Someone at a barbecue is going to tell you that renting is throwing money away. They are wrong in a specific, calculable way, and you can prove it with a spreadsheet.
Take a $600,000 loan at 6.5% over 30 years. In year one, your monthly principal and interest payment is $3,792. Of that, $3,234 on average is interest, and only $559 is principal. Run the full first year: you pay $45,509 in principal and interest combined, and $38,803 of it, 85.3%, is interest. That money is gone. It doesn’t build equity. It doesn’t come back when you sell. It’s functionally identical to the check you’d write a landlord, except your landlord is a bank and the “rent” is called interest.
The honest version of “renting is throwing money away” is: some of what you pay to own is also gone forever, and it’s usually most of your payment for the first decade or more. Once you accept that, rent vs buy stops being a moral argument and turns into what it always should have been: a math problem with a specific answer for your specific situation.
Let’s do the math.
The Costs Nobody Puts in the Mortgage Calculator
Every online rent-vs-buy calculator starts with principal and interest and stops there, which is why they’re mostly useless. The real monthly cost of owning a home includes:
- Property tax: commonly 1% to 1.3% of the home’s value per year, depending on your county
- Homeowners insurance: rising fast in a lot of metros, easily $1,500 to $3,000+ a year
- Maintenance: budget roughly 1% of the home’s value per year. Roofs, water heaters, HVAC, the stuff that breaks on its own schedule, not yours
- HOA dues: $0 if you’re lucky with a single-family home, $200 to $600+ a month if you’re not
- Closing costs on the way in: typically 2% to 3% of the purchase price, loan origination, title insurance, escrow, inspection
- Realtor fees and closing costs on the way out: typically 6% to 8% of the sale price when you sell
None of that shows up in the “$3,792 a month” headline number, and all of it is real cash leaving your account. Add property tax, insurance, and maintenance to the mortgage payment above and a $750,000 house with 20% down runs about $5,255 a month before you’ve spent a dollar on a plumber emergency or an HOA special assessment.
The Breakeven Horizon: Why a Short Stay Should Never Buy
Buying and selling a house both cost money, separate from the mortgage. On our $750,000 example, closing costs to buy run about $18,750 (2.5%). Selling two years later at a modestly appreciated $795,675 costs roughly $55,700 in realtor fees and closing costs (7%). Add those together and you’ve spent about $74,400 just moving the house in and out of your name, against only $45,675 of price appreciation over those two years.
That’s the breakeven horizon in one sentence: at 3% annual appreciation, it takes roughly three years of pure price gains just to cancel out a 9.5% round-trip transaction cost, before you’ve paid a cent toward mortgage interest, tax, insurance, or maintenance. If you know you’re staying less than three years, the math is not close. Rent.
This matters more for tech workers than almost anyone else, which we’ll get to in a minute.
The Down Payment’s Opportunity Cost
Here’s the piece most rent-vs-buy takes skip entirely: that down payment is a lump sum you’re choosing not to invest.
Put $150,000 down on a $750,000 house plus $18,750 in closing costs, and you’ve committed $168,750 to a house instead of an index fund. Invested at a 7% average annual return, that same $168,750 grows to about $270,976 over seven years, untouched, with no landlord, no leaky roof, and no HOA board meeting.
That’s not a hypothetical cost. It’s the return you gave up in exchange for the roof over your head, and it belongs in the comparison whether or not anyone’s calculator includes it.
Price-to-Rent Ratio: The 30-Second Screen
Before you build a full spreadsheet, there’s a fast gut check: divide the home price by the annual rent for a comparable place.
$750,000 house, $2,800/month comparable rent, so $33,600 a year. $750,000 divided by $33,600 is 22.3.
The rough rule of thumb: under 15, buying usually wins. 15 to 20, it’s close and depends on your specifics. Above 20, renting usually wins, because the market is pricing homes at a level where rental yields don’t justify ownership on cash-flow terms alone. A ratio of 22.3 is a market screaming “this is a renter’s market,” and the full math below backs that up.
The Mortgage Interest Deduction Is Worth Less Than You Think
People still act like the mortgage interest deduction is a major subsidy for buying. Assume a joint standard deduction around $30,000 for 2026, adjusted for inflation each year. Your $38,803 in year-one mortgage interest is fully deductible (the loan is under the $750,000 cap), so if you itemize, you get $38,803 worth of deductions instead of taking the $30,000 standard deduction automatically.
The actual benefit of itemizing is the difference: $38,803 minus $30,000 is $8,803 of additional deduction. At a 24% marginal federal rate, that’s about $2,113 in tax savings for the year, not the “I get my mortgage payment subsidized” story people tell themselves. And if you live in a state with income tax, you’ve likely already used up your $10,000 SALT cap on state income tax alone, so property tax adds nothing further. Worse, that $2,113 benefit shrinks every year as your interest portion falls, and by the back half of a 30-year loan it usually disappears below the standard deduction entirely.
The Job-Mobility Tax on Tech Workers Specifically
A layoff, an acquihire, a better offer from a company two states over: any of these can mean a metro change, not just a job change. For a renter, that’s a 60-day notice and a moving truck. For an owner, it’s the 9.5% round-trip transaction cost from the breakeven section above, paid on demand, on whatever timeline your career decided for you.
If you took a job in a new city 18 months after buying, you’re not just moving, you’re eating a transaction-cost loss that a renter in the identical situation never sees. The flexibility premium renting buys you is worth real money if your career has any chance of moving you, and in tech, it usually does.
The Worked Example: $750,000 House vs. $2,800 Rent, Seven Years
Here’s the full comparison, one set of assumptions, verified with a spreadsheet rather than vibes.
Assumptions:
- Home price: $750,000, 20% down ($150,000), $600,000 loan at 6.5% fixed for 30 years
- Monthly principal and interest: $3,792
- Property tax: 1.1% of price/year ($8,250), insurance: $1,800/year, maintenance: 1% of price/year ($7,500), no HOA
- Total monthly cost of owning: $5,255
- Closing costs to buy: 2.5% ($18,750). Selling costs at exit: 7% of sale price
- Home appreciation: 3%/year. Comparable rent: $2,800/month, growing 3%/year
- Renter invests the $168,750 (down payment plus closing costs) and every month’s cost difference between owning and renting, at a 7% average annual return
- Holding period: 7 years
Owner’s outcome at year 7:
- Sale price: $922,405
- Selling costs (7%): $64,568
- Remaining mortgage balance: $542,497
- Total interest paid over 7 years: $261,060 (never coming back)
- Owner’s equity at sale: $315,340
Renter’s outcome at year 7:
- $168,750 lump sum invested, grown at 7%: $270,976
- Monthly difference between owning ($5,255) and renting ($2,800, growing with rent inflation) invested along the way: $237,238
- Renter’s total portfolio: $508,214
The renter comes out $192,874 ahead after seven years, in a scenario where the house also appreciated the whole time. Change the assumptions (lower price-to-rent ratio, higher appreciation, longer hold, cheaper mortgage rate) and the gap narrows or flips. Run your own numbers before repeating a rule of thumb you heard from a realtor.
Buying Is Partly a Lifestyle Decision, and That’s Fine
None of this means renting always wins or that owning is a mistake. A house you actually own is a hedge against a landlord raising rent 12% at renewal, a place you can renovate without asking permission, and a fixed housing cost that inflation slowly erodes in real terms over 30 years. There’s real value in stability, in a school district, in a yard, in not moving your furniture every two years. Those are legitimate reasons to buy a house that a spreadsheet will never fully capture.
What the spreadsheet does capture is whether you’re paying a fair price for that stability. In a market with a price-to-rent ratio over 20, you’re paying a steep premium for it. In a market at 12 or 13, that stability is closer to free.
The Verdict
Run your own price-to-rent ratio first. Above 20, rent and invest the difference unless you have a specific, non-financial reason to buy anyway (kids in a school district, a partner’s career anchor, a genuine desire to never move again). Below 15, buying starts to make financial sense on its own terms, assuming you’re staying at least five years to clear the transaction-cost breakeven with room to spare.
And regardless of the ratio: if you can’t commit to staying three years, don’t buy. The transaction costs alone will eat you, before the mortgage, the maintenance, or anything else gets a chance to.
The barbecue guy isn’t entirely wrong that money disappears either way. He’s wrong that it’s a bigger amount when you rent. Run the numbers for your city, your rent, and your timeline, and let the spreadsheet tell you what your gut can’t.
