It.. doesn't work like that. Suppose someone sells you a private key, or even a hardware wallet, claiming that it "contains much Bitcoin". There's no way for yo

It.. doesn't work like that. Suppose someone sells you a private key, or even a hardware wallet, claiming that it "contains much Bitcoin". There's no way for you to be sure that the seller doesn't have a backup. Or is selling ten other copies to other people. It's like trying to sell an account by selling the password to it. The first thing you do is change it so the previous owner can not get in anymore. Before you did that you can not be sure that you are the only one with access. On Bitcoin the only way to change the password is to move the funds to a new address.