My advice is to never loan money to friends or family unless you can truly reconcile in your mind that if they don't pay it back, you will make it a gift to them and not destroy your relationship. You may also need to resolve that it may destroy the friendship anyway.
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That said, if your gut tells you to loan him the money, consider what his alternatives are if you weren't there to help him. He likely has bad credit if he can't get a credit card or bank loan to cover $10K. Credit cards for great credit are hovering around 12-20%. If his credit is a bit dodgey it will be much higher than that. If you are good friends and really want to give him a break, give him a 5-8% loan. If you want to make a little money off of the deal, I'd say 10-15%.
In 2001 my father loaned me $10K to start my first business at 8% interest. It was equal to the going rate for an SBA loan at the time. He never asked for a single payment, but I paid him off in full 2 years later. You may want to check out what SBA loans are going for these days. Suerte.