Rent or buy in Boise? How to run the numbers on a real house

Last week I wrote about when you shouldn’t buy a house in Boise. The most common reply I got was some version of: “Okay, but how do I know which one I am?”

Fair question. Slogans like “rent is throwing money away” or “marry the house, date the rate” don’t answer it. A spreadsheet does. So I built a rent vs. buy calculator that compares buying a specific home with renting a similar one and investing the difference, using today’s rates and Treasure Valley costs.

Try a quick version right here, then I’ll walk through a real example and what actually moves the answer.

Why “rent vs. mortgage payment” is the wrong comparison

Most people compare their rent to a mortgage payment. If the payment is close, buying feels like a no-brainer. But that comparison leaves out almost everything that matters:

• The payment isn’t the whole cost. Taxes, insurance, HOA dues and mortgage insurance come on top of principal and interest. Then there’s maintenance, which a lender never quotes but you’ll definitely pay.
• Part of the payment is savings. The principal you pay down comes back to you when you sell. Interest doesn’t.
• Your down payment has a cost too. Cash tied up in a house isn’t earning anything anywhere else.
• Getting in and out is expensive. Closing costs when you buy plus selling costs when you leave can total 8% of the price or more.

The better question is: after the number of years I’ll actually live there, which choice leaves me with more money? That’s what the calculator answers. Each month it figures out whether owning or renting costs more, assumes whoever pays less invests the difference, and compares your net worth at the end.

A real example: a $450,000 home in Meridian

Here’s the calculator’s default scenario. It’s a reasonable picture of a three-bedroom house in Meridian today, not a specific listing:

• $450,000 purchase price, 10% down, conventional 30-year fixed at 7.40%, the national average in Freddie Mac’s survey for the week of October 8, 2026
• Comparable rent of $2,300 a month, close to Rentometer’s early-2026 median for a three-bedroom house in Meridian
• Home values rising 2% a year. For context, Zillow’s typical Ada County home value was up 1.6% over the year through September 2026.
• Rent rising 3% a year, a 5% return on invested savings, 2.5% buyer closing costs, 6% selling costs, a 1% maintenance budget, and a 7-year stay

First, the monthly picture. The payment a lender would quote is about $3,392: $2,804 principal and interest, $236 property tax, $133 insurance, $50 HOA and $169 private mortgage insurance. Add $375 a month for maintenance and the real cost of owning is about $3,767, compared with about $2,315 for rent and renters insurance. Buying also takes about $56,250 in cash up front.

Over those seven years, the buyer pays about $33,600 in principal, which builds equity, and about $201,900 in interest, which doesn’t. Selling costs take roughly $31,000 more off the top. The renter, meanwhile, invests the $56,000 they didn’t spend on the down payment and closing, plus about $1,450 a month in savings.

Here’s how that gap changes with time in the home, under the same assumptions:

At 2% appreciation and a 7.40% rate, buying this home doesn’t pull ahead until about year 26. The calculator also works backward to two break-even numbers that are often more useful than the verdict itself:

• Break-even rent: about $3,120 a month. If a comparable home rents for more than that, buying wins over seven years.
• Break-even appreciation: about 4.5% a year. Prices would need to rise at least that fast for seven years for buying to come out ahead.

I want to be clear about what this does and doesn’t mean. It doesn’t mean nobody should buy in Meridian. It means this house, at this price, this rate and this rent, is a tough financial case for a seven-year stay. Change the inputs and the answer changes, sometimes a lot.

What actually changes the answer

Here’s the same seven-year example with one assumption changed at a time:

Three things jump out to me:

Time matters most. Buying starts in a hole because of closing costs and the cost of selling. The longer you stay, the more time you have to climb out. That’s why the years-you’ll-stay input deserves your most honest answer.

Appreciation is the biggest wild card. The difference between flat prices and 4% a year is about $129,000 in this example. Nobody, including me, knows what Treasure Valley prices will do over the next seven years, so the calculator shows a grid of outcomes instead of betting on one number.

The rate matters, but less than you’d think. Dropping from 7.4% to 6.0% helps a lot, yet in this example it still doesn’t flip the result at seven years. That’s one reason I don’t love “buy now, refinance later” as a plan.

Does the loan type change anything?

The full calculator handles conventional, FHA, VA and USDA loans, including each program’s upfront fee and mortgage insurance rules. Low-down-payment loans change when you can buy more than whether buying wins:

• FHA with 3.5% down: about $27,000 in cash instead of $56,250, but a 1.75% upfront premium is added to the loan and, with less than 10% down, the annual premium lasts for the life of the loan. Total monthly cost rises to about $4,056, and renting is ahead by about $109,000 after seven years.
• VA with 0% down: about $11,250 in cash (closing costs only) and no monthly mortgage insurance, but a 2.15% first-use funding fee is added to the loan. Renting is ahead by about $97,000 after seven years.

None of that makes FHA or VA bad loans. They’re how a lot of people get into a home years sooner, and if you’re planning to stay a long time, that can be worth a lot. If cash is your main hurdle, my guide to Idaho first-time homebuyer programs is worth a read too.

Should you consider a 5- or 7-year ARM?

An adjustable-rate mortgage gives you a fixed intro rate for five or seven years, then adjusts periodically within caps. With rates where they are, I’m getting this question more often, so the calculator models both.

Say a lender quoted a hypothetical 7-year ARM at 6.5% on the example home. Principal and interest drops from $2,804 to about $2,560 a month. If you sell before the rate ever adjusts, it behaves just like a 6.5% fixed loan: renting is still ahead after seven years, but by about $58,000 instead of $87,000.

The catch is the worst case. With common 2/1/5 caps, the rate on that loan could eventually reach 11.5%. If it did, the calculator puts principal and interest at roughly $3,760 a month, nearly $1,000 more than the fixed loan. With a 5-year ARM the reset comes two years sooner.

My take: an ARM can make sense if you’re confident you’ll sell or refinance before the first adjustment and you could live with the worst-case payment if plans change. The calculator shows you that worst case every time you pick an ARM, because it’s the number I’d want you to look at before signing.

What a calculator can’t tell you

The model is only as honest as its assumptions, and some of them deserve a second look:

• It assumes the renter invests the difference. If you’d honestly spend that $1,450 a month, renting looks a lot worse. A mortgage is a kind of forced savings, and that has real value for many people.
• It can’t price stability. A landlord can sell or raise the rent. You can’t paint, renovate or get a dog without permission. Staying near a school or family has value no spreadsheet captures.
• It can’t predict prices or rates. It shows a range of outcomes so you can see how much you’re betting on each.
• Taxes are simplified. Most buyers take the standard deduction ($32,200 for married couples filing jointly in 2026), so the mortgage interest deduction often saves less than people expect. The calculator has an optional section if you itemize, but check with a tax professional.

How to run it on a house you’re actually looking at

Five minutes of homework turns a rough estimate into a useful one:

1. Find the real comparable rent. Look at what homes of similar size, age and location rent for, not your current apartment.
2. Look up the property tax bill on the Ada or Canyon County assessor’s site, and remember the homeowner’s exemption if you’ll live there.
3. Get an insurance quote and confirm HOA dues.
4. Use a lender’s loan estimate for the rate, loan type and, for an ARM, the caps.
5. Be honest about how long you’ll stay. Then try a shorter number too, because life happens.

When you’re done, the calculator’s “Copy a link to these numbers” button saves your whole scenario in a link you can send to a partner, or to me.

Open the rent vs. buy calculator

The bottom line

Renting isn’t throwing money away, and buying isn’t automatically an investment. At today’s rates, a lot of Treasure Valley homes need a longer stay, stronger price growth or a higher comparable rent to beat renting on pure dollars. For other homes and other buyers, the math works fine, especially if you’ll stay a long time and value what owning gives you beyond money.

The point of running the numbers isn’t to find a reason to say yes or no. It’s to know what you’re trading. And if the numbers don’t work for you, I’ll tell you.

All dollar figures are illustrative estimates from the rent vs. buy calculator using the assumptions stated above and rounded. They are not a loan offer, appraisal or forecast. The ARM rate is hypothetical. This article is general information, not financial, tax or legal advice; talk with a licensed lender, your tax professional and your financial advisor about your situation.

Sources

• Freddie Mac — Primary Mortgage Market Survey (week of October 8, 2026)
• Rentometer — Average rent in Meridian, ID (early 2026)
• Zillow — Ada County home values (through September 30, 2026)
• U.S. Department of Veterans Affairs — VA funding fee rates
• JVM Lending — FHA mortgage insurance premiums in 2026
• Kiplinger — 2026 standard deduction and SALT cap