What happens, though, when the home you think is your starter house becomes your forever house?

As first-time home buyers, we often cobble together what we have for a down payment with the expectation that in five years (because, face it, we like to believe that life operates on an endless loop of five-year plans) we’ll upgrade to something larger, or in better condition, or in a better neighborhood. Realizing that we may not actually be able to move runs counter to an American ideal that there’s always a better version of our lives a few pay raises away.

“We are restless people, we like to feel like we could move at any time. If you think of your house as your starter home, you know you can just leave,” said Melody Warnick, the author of “This Is Where You Belong: Finding Home Wherever You Are.” “That’s a belief that we cherish because it gives us a sense of freedom.”

But increasingly, the math doesn’t work and we find that we’re not so free to go.

A brew of short- and long-term trends has led us to this moment. Millennials, saddled with student debt, are buying their first homes later in life, and so are less likely to move again. Inventory is tight (largely because homeowners aren’t moving), home prices are high, and interest rates are rising.

Added to that, the 2017 federal tax overhaul capped the mortgage interest deduction at $750,000 and limited sales and local tax deductions to $10,000 a year, making it less desirable for owners in high-tax states like New York to buy a home with a jumbo mortgage or a giant property-tax bill.

In short, if you were lucky enough to lock in a historically low interest rate, whatever you buy today will cost you more than it did just a few months ago. The Lassers, for example, pay roughly $12,000 a year in property taxes for the six-bedroom house that they bought for $1.475 million in 2016. But if they decided to move to the suburbs, their property taxes would likely be higher, and if they bought a house priced at or more than what they paid for their current home, their monthly mortgage payments would be substantially higher at current interest rates.