Are there any banks that give mortgage loans to people with bad credit?

I am looking to buy my first home. My goal is to get to a 620 credit score but I know this will take quite some time. I was wondering if there are banks out there that give you loans to buy a home if you have bad credit or if there are programs out there that help you fix your credit to get into your first home? My best credit score of the three credit agencies is 550. The worst is 490. Please help!