If i have a credit score in the 500's and co signer 750 what can i hope for on my mortgage loan?

I know my mom had excellent credit she only had one small bill unpaid on her credit that she had to pay before she could purchase a home, and she had excellent credit, But I believe anything lower than 600 is really difficult, but not impossible, there are programs for lower credit scores but you'll have a higher interest rate...hope this helps...good luck, Kimberly