One thing to consider is that while yes, if you have a co signer with good credit, they will use the beter of the two, they wil also require documentation from the co signer, usually pay stubs, bank statements, and the like. This may vary depending on which company doing the lending, but if I used a co signer with sallie mae or wells fargo private law loans, they would have required my husbands pay stubs and all that. Not that it is a big deal when it is my husband, but if I had to get that stuff from my parents, it might be more of a hassle.