yes, its linked.
Yes, it is linked and any bans given to him will also be given to you unless removed. Also if he actually still plays the game online or gave/sold *anyone* his CD-key, you may have problems playing online.
I don't know how much he asks for it, but buying the game new is not that expensive any more. It depends on where you live but you can get it new as cheap as 15 euros.