Don't do it!!!
When you co-sign on a loan you are legally responsible for it if the other person stops paying on it for whatever reason. So that means if you co-sign for your best pal, then he gets in an accident and is in the hospital, unable to work and pay his bills, guess who will start receiving phone calls from creditors? You.
There can also be bad blood when you get financially involved with something like this. Look at this:
I co-signed for a student loan for my daughter with the understanding that she would help pay off some of the amount owed. It has been four years and she still hasn't paid anything.
Yikes! I can't even imagine what dinners together must be like for this family!