Chances of getting a mortgage with a low credit score but have 20% down, & a co-signer?

Currently, I'm renting a 1 bedroom apt. I've found a 2 bdrm condo I'd like to buy. Even with the mortgage payment, utilities, taxes, & insurance, its about the same amount of money that I'm currently paying in rent. So its not an issue of whether I can afford it. But my credit score is only in the low 500s. I've only been at my job for 2 years, before that I was in school. As I said, I have 20% cash to put down. My co-signer is my grandmother, who has no debt. She's a small business owner, which the business has no real debt, maybe a few thousand owed to vendors at any given time. The building the business is paid off, as is her house & car. Will her credit help me enough to qualify for a loan?