What follows is an excerpt from my new book, Starting Strong: Discovering the Good That Money Can Do in Your Marriage.

A national survey of over 900 recent homebuyers found that a whopping 82% had regrets about their purchase. One of the top regrets was simply spending too much on the house.

Mortgage lenders use two ratios to determine how much of a mortgage you can afford. The first one compares the combination of your monthly mortgage payment (principal and interest), property taxes, and homeowner’s insurance (PITI) with your income. Typically, lenders want PITI to take up no more than 28% of your monthly gross income. The second ratio adds in all of your other debts, such as any credit card balances you carry from month-to-month, vehicle loans, and student loans. Usually, a lender wants your housing costs plus these other debts to require no more than 36% of your monthly gross income.

A better number

Here’s what I recommend: Devote no more than 25% of your monthly gross income to the combination of your mortgage, property taxes, and homeowner’s insurance—preferably no more than 20%. And have no other debt.

In especially high-cost parts of the country, you may need to devote 30% of monthly gross income to housing, but I wouldn’t go any higher than that. Of course, that means you’ll have to spend less in other areas, such as vacations or entertainment. (There are more detailed income-based recommendations for how much to spend on a house in the the resources section of my website.) If you are renting, keep the combination of your rent and renter’s insurance to no more than 25% of monthly gross income—preferably 20%.

Here is one really important—and, I realize, challenging—caveat. Try to make these numbers work on one income.

Delusions of DINKhood

If marriage will turn you into a DINK (double-income, no-kids) household, it’ll be tempting to live it up. Just think of the house you’ll be able to afford, the cars, the trips, and the nights out!

I don’t mean to rain on your parade, but before you start dreaming of all that, consider this: Do you want to have children some day? If so, would you want the option of having one of you step out of the paid workforce to stay home with your children? Making sure your monthly housing costs (mortgage, real estate taxes, and homeowner’s insurance) requires no more than 25% of one income—preferably no more than 20%—will be the single biggest factor that will enable you to do that. Even if you don’t plan to have kids, it’s wise to base your housing costs on one income. Otherwise, what if one of you lost your job?

I once met with a husband and wife who, by outward appearances, had a wonderful life: two newer (leased) cars, frequent dinners out, and a beautiful home (with a mortgage that required a large portion of their combined high incomes). Then she lost her job. When we met, their faces were full of fear. His had a tinge of anger. They were under a lot of stress and he seemed to think it was her fault. But it wasn’t. They had both chosen that high-risk path.

The best financial advice Jude and I received before getting married was to base our lifestyle primarily on one income. We gave from our combined income, but we bought our condo based on what we could afford on my income alone. That enabled us to focus Jude’s income on boosting our saving and investing, knowing that our ability to do both would be reduced if and when we had kids and she stepped out of the paid workforce. It also enabled us to take some great trips. Before having kids, we went to Europe several times.

Four years into our marriage, shortly before Jude got pregnant with our first child, she left her paid job. Because we could afford our condo on my income alone, it was relatively easy for us to go from two incomes to one.

Dare to be different

Buying a home based on one income is very counter-cultural. It’s not the world’s way. It may not be what your friends are doing. And that’s what can make it difficult. But if you do, you will be mightily blessed. You’ll be able to give generously while saving and investing appropriate amounts for the future. And you’ll be able to enjoy one of the most wonderful financial experiences possible: margin—a beautiful, peace-of- mind-inducing gap between your income and expenses.

Again, this won’t be easy and it won’t be normal. But don’t settle for normal. Normal is financial stress and strain. Normal is wondering why there’s never enough. Normal is wishing you could be more generous. Normal is knowing you really should be saving and investing more. Normal is believing that if you just made more money…

Choosing a home you can afford on a single income is one of the absolute best money moves you could make.

If you’re engaged or newly married, or if you know a couple that is, pick up a copy of Starting Strong: Discovering the Good That Money Can Do in Your Marriage. I wrote it to help couples get their marriages headed in a good, God-honoring, marriage-strengthening direction.