Changing ownership of account is allowed, not sure about "buying" it, thou if you don't say anything, they wont know if it was purchase or gift.
Having two character on the same server, however, is technically not allowed. Thou the reason given is that it can be used in ways that violate the spirit of the game (i.e. cheating) whereas nowhere does it say that having two char on the same server in and of itself is not allowed. Given that, sage enablers(that does nothing else but enable sage) have generally been considered on the ok side. That, however, is probably not your intended use for the account, so technically speaking, no it is not ok.