buying steam account = ban of your legitimate account(s)
Care to elaborate?
I have juggled with half a dozen accounts and am using two now (one was bought) and no problems.
Yes, IF they find out you bought/sold an account it will probably be disabled... but unless zer0 posts the user name/nick name and someone reports him to VALVe I see no problems whatsoever. Just wait at least a day before you log in after buying it if the buyer lives far away from zer0.