From what I recall when I got one last Sept it say's on the invite they are non-transferable so not sure if buying one would work as you need to type-in the invite code number which they likely later match up to the persons name and address. Even if you use the same name as on the Invite do you really want your check issued to someone else?
Update all the contact info to their name, update it with their tax id, give the person your user/pass so they can log in and confirm all the changes and make sure the password is changed.