“House poor” is a common expression used to describe people who are wasting too much money on housing, leaving them with too little to spend on everything else. But it can also refer to those who are getting too little housing bang for their buck.

And now, with interest rates on home mortgages spiking faster than they have in decades, it’s getting more expensive by the moment to own a home in the U.S.

As an economist, one of my goals is to make you “house rich,” ensuring you end up with the housing you really want at the price you can really afford.

Here are some ways to lower your housing costs:

Young Americans are increasingly aware that shacking up is a moneymaker. In fact, a handful are now living with their parents.

This is a massive change from the way things were in 1960, when only 29% of young people camped out with mom, dad, or both. The counterpart of this change in living arrangements is that older many Americans are living with their kids and, possibly, their grandkids.

Sure, rooming with your folks likely won’t entail proportionate sharing of dollar expenses, but if your parents or grandparents really seek your companionship, the living arrangement can be viewed as you paying your fair share of rent and them paying for your company.

The net payment is, then, what you can actually fork over for board.

You can do this on a part-time basis. Airbnb and similar online companies have made this very easy.

A cousin of mine lives near the beach in Los Angeles. As house prices and property taxes soared, the imputed rent — or the sum of property taxes, homeowner’s insurance, maintenance, and forgone after-tax interest — became unaffordable.

One option was to sell and find cheaper housing in the suburbs. The other was to transform her garage into a studio apartment and rent out her house on Airbnb. She chose the latter route, and over five years, has pulled in enough income to significantly upgrade her studio apartment as well as the house.

Since Airbnb rents are very high in her area, she can rent her place during the year and garner the same financial gain as if she had a full-time roommate. But this arrangement gives her much more privacy and lets her rent to larger-sized families who don’t want an unfamiliar roommate while on vacation.

There are 42 states, plus the District of Columbia, with income taxes. The states that don’t tax income are Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington and Wyoming.

If you live directly on the Massachusetts-New Hampshire border, you can, theoretically, move across the street and save 5% of your pay, which you’d otherwise surrender in Massachusetts income taxes.

Things are more complicated, of course. Land values in New Hampshire may be higher in light of the state’s tax advantage. And amenities, like the school system, may be better in Massachusetts. But who knows? You may be childless and happy to live in a five-decker with no yard.

Another consideration in deciding what home in what state is estate taxation. In addition to D.C., 11 states levy estate taxes: Connecticut, Hawaii, Illinois, Maine, Massachusetts, Minnesota, New York, Oregon, Rhode Island, Vermont and Washington.

Another five states, Iowa, Kentucky, Nebraska, New Jersey and Pennsylvania, tax inheritances. And one state — Maryland — taxes both estates and inheritances.

If you have significant wealth you’re likely to bequeath, be careful about spending your golden years in states with estate taxes.

If it’s not practical to share or rent out your home, consider downsizing to less costly housing that still suits your needs.

Americans have large homes. In fact, the majority of recently constructed homes have three or more bedrooms. Having lots of rooms when you’re raising kids makes sense. But after they’ve left the nest? That’s a prescription for overspending on housing.

Yes, holding on to a house gives you a built-in safety net — a store of value that you can eventually swap for entry into a long-term care facility. But every year you pay too much in imputed rent is a year you’ve wasted money.

Paying for something you don’t need to mitigate a specific future financial risk isn’t necessary. There are other ways to deal with long-term care needs. One is to buy long-term care insurance. A second is simply to hold financial assets, including real estate, but indirectly in the form of real estate investment trusts (REITs).

A third is to arrange for your children to care for you if you need assistance short of skilled nursing. This can be quid pro quo.

For example, you might downsize, then use freed-up equity to provide your children with down payments to buy their own homes. In exchange, you can make it clear that you expect them to take care of you if you need help down the road.

Laurence J. Kotlikoff is an economics professor and the author of “Money Magic: An Economist’s Secrets to More Money, Less Risk, and a Better Life.” He received his Ph.D. in economics from Harvard University. His columns have appeared in The New York Times, WSJ, Bloomberg and The Financial Times. In 2014, The Economist named him one of the world’s 25 most influential economists. Follow Laurence on Twitter @Kotlikoff.

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