The other point I'd like to make is this....If you have poor credit, fixing that should be your top priority. Only by having good credit will you be able to take advantage of the low rates currently available.
Poor credit usually comes from not paying other debts, having unpaid credit card balances, an erratic history of paying off debts, etc. You might not appreciate this, but you'd be wise to pay off these back debts first before incurring something as large as a mortgage.
All the best.
You may be able to get a loan with a low credit score with in reason say 640 for FHA loan; however other factors must be looked at (income,debt, credit worthiness,your lender will discuss these matters with you). But if your score is very poor, you should not set yourself up for failure. Should you go to a lender and find that you are not able to get a loan at this time, ask what stopped you and start working on that. Also ask your lender for a credible debt counseling agency. Put yourself in the most favorable light and get what you deserve and want. Don't settle for less!
Thanks for question and take care!
Doris J. Bailey, GRI, AHWD, Broker