If your credit score isn't any good, don't count on getting a mortgage. I have told people that time and again! Recently a friend told me her credit score was under 500 and she thought it was due to the bankruptcy she had 12 years ago. She wants to refinance her mortgage but with her credit score, she is unable to do so.
My first question was to ask her what credit cards she has. Response: none. I asked her if her current mortgage payments and car loan payments are on time. Response: car is paid off and mortgage payments are generally on time.
My advice to her was to make sure ALL of her mortgage payments are on time or even early if she has trouble remembering to get the check in the mail. I also advised that she get a credit card! Target will generally give just about anyone a credit card, so I suggested she begin there and if Target refused to give her credit, go to her local bank and get a prepaid credit card.
In addition to having a credit card, I explained that her balance should always be UNDER 30% of her credit limit. Use it and pay the balance off each month but never charge above 30% of the credit limit. I explained that you need to show a history of paying your credit bills on time in order to bring those scores up.
So many people have no idea how to help themselves improve their credit score and if you know what to do, it is relatively easy to get that score up.