LOL 15% +..... Fuck that you greedy asshole. People like you make me sick. I hope the buyer does a charge back that would be karma.
15% is probably a little bit on the high side if he is only willing to deal with trustworthy people, however it is a free market and he is probably targeting people who want to quickly have access to funds when selling bitcoin.
The fact that he is looking for reputation means that he is looking for someone who has a tendency to do business honestly so the risk of chargebacks for him would be low.