NEW YORK ( TheStreet) — Once you find the perfect home, secure financing and sign the contract, you may be ready to pop open some champagne and start picking out curtains. Be careful, though. There are several mistakes you may make as a would-be homeowner that will derail a closing or drive your interest rate higher.

When you apply for a mortgage, the first credit check your lender runs won't be the last. Another credit check is performed just before you close. If there are negative changes in your credit score, you could be saying goodbye to your dream home before you ever put the key in the door.

1. Change in job status

Banks want stability, and if you show them you're changing jobs at such an important time in your life, they may think twice about offering you a mortgage.

"A change in job status from part time to full time is fine, but not the other way around," says Greg McBride, chief financial analyst for Bankrate.com. "Going from employee to contractor, or salary to commission, it's just not a good move."

Read More: How You Know It's Time to Stop Renting and Buy a Home

If you're moving to a better job with a higher salary, the change won't torpedo your closing, but it might delay it.

"You would be required to show new paystubs, even if you're moving to a much better job," he says.

Changing positions within the same company is not likely to raise red flags as long as your salary stays the same.

2. Making late payments of any kind.

If you have a mortgage on your current property, missing a payment during this time could cause serious problems, says Peter Grabel, managing director of Luxury Mortgage in Stamford, Conn.

"One late payment will not only kill your score, it will make you ineligible for a loan with most lenders for at least a year," he says.

It's not just mortgages. Even something as innocuous as a utility bill can do damage. Unfortunately, if you're planning a major move, it's easier than you might think to let bills fall through the cracks, says Jacky Teplitzky, a broker with Douglas Elliman in New York City.

"This sort of thing won't show immediately. The utility company has to report it, and the process takes time. But there are scenarios where it can weaken your position," she says.

For example, if you've already moved and your mail forwarding service hasn't kicked in, a missed bill may never make it to your door. Or if you sublet your old place and the tenant has failed to pay the utilities, those negative reports could find their way to your credit score.