The real problem here is attaining that "full, proper site and a reputation." Getting those two elements in place could take years of work, some of it completely unpaid. I suspect the OP doesn't have either of those, and is using this as a way to build up some kind of portfolio (and certainly a lot of online visibility, which can be surprisingly hard to come by) as rapidly as possible while still pulling in some income.

Not that he needs to use any of the $15 work directly in his portfolio -- but if he hashes out lots of designs in a creative way, he's going to end up with some obvious winners that he can polish up.