You have to work on your credit. You may want to call The Tejano Center 713-6496201, they offer credit counseling and HOmebuying Education classes for First Time buyers, and if you want a grant to match your savings for down payment assistance, you need to call the Covenant Program 713-2231864. Both are great palces to start and help you on your credit, both are non-profit agencies.
Good Luck to you!!!