I used to do that for people where I used to live. They weren't friends but, I charged all the Ebay listing costs, sellers percentage and the cost for packaging, i.e boxes, tape, bubble wrap etc., plus I charged 5-10%. If it was a large ticket item (over $100) I charged them 5% and 10% if it was a smaller ticket item (100$ and under). It really is quite a lot of work so I would have probably charged the same if it was a friend or relative as well. They should understand that. If they don't I wouldn't do it for them. That's my opinion. I hope it helps give you an idea of what to do. What ever you decide you really need to get the details worked out before you start or it could cause some hurt feelings in the end. Good Luck.