Is it worth to buy a iPhone 3GS for 115$?

Me and a friend of mine found it left over in the middle of the street and I grabbed it.. I broke the SIM Card, and I reset the phone, now my friend is saying that if I want the phone for me I'll have to give him 115$ cause that would be what he was going to earn if we sold the phone. Should I keep the phone and give him the 115$ ??