After reading [link] I'm wondering : is selling fanart wrong? '____' because I have to admit, I'm not very creative when it comes to thinking up of original ideas / characters / concepts. Almost everything I draw/sell IS fanart!

Is is an infringement of copyright? - seeing as how one uses someone else's characters to gain profit. Or is it a way of "advertising" for the series? In that case, is it okay to sell fanart, provided due recognition is given to the original creator, eg : including something like " [title/character's name] belongs to [creator's name] " ?

As for commissions, what if someone requests a drawing of existing characters? What / how then? '___' ;;;;;;