Good, you want to sell stuff, fine. But USED Mc accounts? No offence here, but mate, they may be stolen or someone can clam em back as mentiond by some people here.
Not to offend you, but I want to "warn" people that CAN somethimes happen with "used" accounts.
Plus minecraft accounts now most of them are assigned to an email address that you can never change.
visit mojang.com, change email address?
i've done this many times, it is still possible.
the kid can still recover the account using proof of purchase if you buy from him, so beware