Legal in the sense that there isn't a law prohibiting it, yes it is legal. After all, there is no particular government that is monitoring or supervising the activities here. But whether it is allowed here in the forum itself, I guess it is not. But I am confused why a lot of accounts are offered for sale here. I don't understand. But if you are interested in buying one, I advise you not to proceed. Many of these are most probably hacked accounts and you do not know the quality of accounts either. You better be patient and use a single account made by yourself alone.