You’ve had some rough patches financially. A divorce a few years ago messed up your credit score because of bills that didn’t get paid beyond your control. A few unpaid credit card bills here and there just added to the less-than-stellar number.

Life. It can get in the way sometimes of having a great credit score, at least temporarily. But if you are hoping to buy a house and get a loan, you might still be in luck even if you feel your credit score seems pretty low.

What credit score do you need to get a mortgage?

How low are we talking about?

“620 is very low, but you can get a loan with it, and it’s the absolute minimum for a Fannie Mae loan,” says Chris Thomas,  loan originator at America’s Mortgage LLC in Wheat Ridge, Colo. “FHA loans will go down to 580 sometimes. But the only things that count against you on your credit report are whatever is listed on your report the last two years, even though they put seven to 10 years of stuff on the reports.”

But even if Fannie Mae accepts 620, most lenders will limit their conventional loans to 640 for extra safety from people defaulting on a loan.

“Research shows that with a 640, you have a much less chance of going into foreclosure. That’s the risk threshold,” he says.

Thomas says many people just don’t understand what their credit score is all about because no one really explained it to them. People just always hear those commercials on television about getting their free credit score, he says.

“First of all, there is no danger of someone with a 490 or less getting a mortgage,” he says. “You just have to pay your bills, folks. And some people just don’t get that for some reason.”

He also says many people don’t understand that the higher their score, the cheaper their interest rates will be.

“Generally speaking, if they have above 760, you will get the cheapest mortgage interest rates,” he says.

Related: The $13,075 Sweater and Other Credit Card Mistakes

However, about 30 percent of Americans are unlikely to get a mortgage because they have a credit score less than 620, according to a recent Zillow Real Estate Research study.

What does a credit score mean

These mysterious credit scores aren’t really so mysterious once you know where they come from and how you can actually get them higher, Thomas says. Credit reports include such information as where you live, how you pay your bills, whether you’ve been sued or if you have had a foreclosure or bankruptcy. That information is then sold to creditors, employers and insurers that use the data to look into your world to see if they can trust you to give you a loan, rent you an apartment or hire you.

The credit score summarizes your credit report in a number form, and it can range from 300 to 850, according to the Fair Isaac Corporation or FICO. The most widely used credit scores by lenders are FICO scores, says Thomas. VantageScore is also available, which just has different criteria on how it summarizes information from the three major credit bureaus.

“Most lenders don’t accept those scores (Vantage),” he says. “That’s a problem for some people, because they are using the VantageScore that they downloaded from their computers, and usually that one is higher than the FICO score.”

But Thomas says that a credit score isn’t the only thing taken into consideration by a lender to give a mortgage. You also have to have steady income and have some assets. However, Thomas says assets aren’t as big a thing as it used to be, and you don’t have to have so much in reserves as before. Lenders just want to know you have the income and a steady job to pay the mortgage monthly.

By getting as much supporting documentation as possible surrounding your credit problems can help a lender see the whole picture of your financial life.  Sharing all details is important. It could have a big effect on whether the lender will approve your loan or not.

Tips to improve your credit score

And if your lender tells you that your credit score is too low, then there are ways to improve it quickly.

“I’ve seen people raise theirs 50 to 60 points in a month,” Thomas says. “It’s all about discipline. Lenders want to know you are responsible.”

If you went bankrupt three years ago, you could have a 750 credit score within a year if you have nothing bad on your credit report, Thomas says.

“You have to learn your lesson. Lenders expect you to learn your lesson. The way you prove that is to pay everything on time, and have a clean record the past 12 months,” he says. “If you are late on a Sears charge card, you aren’t getting a loan because you haven’t learned your lesson.”

Thomas uses credit analyzer software to help his clients find out exactly what they can do and how many points their score will rise with those actions. Every client’s situation is different because everyone’s credit report is different. But some of the things the software has requested of his clients is to actually open up a secured credit card account if the client doesn’t have many accounts. It also has told his clients to pay down a certain amount on a credit card.

“The worst thing you can do is pay down an old collection account. If it’s over 2 years old, it’s not hurting you,” he says.

His advice is simple — “You have to use credit to have a good score.”