While there are plenty of mistakes that can be made during the process of buying a home, there’s one big mistake that many people make — often without even realizing it — after the purchase is complete.

First-time homebuyers are especially prone to this mistake, but experienced homebuyers aren’t off the hook either.

What is it?

It’s deceptively simple: going overboard on related purchases, while forgetting to take total costs and available funds into account.

You see, when you buy a house, your existing furniture may not fill it up, or even fit. You may need or want to replace all kinds of things — everything from light bulbs to fixtures that aren’t your style. Painting and new wall decor are often on the list too, along with things like new or updated landscaping.

If you’ve always lived in an apartment, you may need tools that you’ve never required before. Then there are ongoing expenses like increased utility costs, taxes, insurance, and other fees. And repairs…

Those things can cost a small fortune — a fortune that you may not have been adequately prepared to spend.

Avoid the hit to your wallet

To avoid a big hit to your wallet like that, plan ahead before you buy to be sure you’ll have enough for a few “must do” items, and then exercise restraint on the rest.

Don’t spend your time looking at Pinterest or the glossy magazines that will arrive in your mailbox if all they do is make you want to go out and spend money you don’t have.

While you may want to fill up empty rooms or rip out nasty wallpaper from the 70s right away, you’ll be better off — and less stressed — by waiting for the right time to do so financially.

Your house doesn’t have to be perfect

Your friends and relatives won’t think less of you if your house isn’t perfect right off the bat. No one’s is. In fact, they’ll probably think it’s smart of you not to rush into things and to take your time. Don’t let advertisements like “no interest for 12 months” tempt you into doing things you’re likely to regret later.

A new house is an enormous financial step, so take the time you need to be sure it doesn’t become a millstone around your neck instead of a home you can enjoy.