I do want to purchase an account but I'm not sure how to go about it. I see a signed message saying you own the account is nice, means that it counts as proof that they changed the ownership over to you. But is there anything else or is that the only way to officially get an account? Does changing the email afterwards mean they can't get it back? It's pretty scary to buy an account even if it's only like $5. Nobody wants to pay for something and then have it taken away.
First of all if you have access to know the account username you want to buy then try search for its all posts, if there is any pending loan of it, any scam accusation etc. Otherwise require this from the escrow to check it for you. Once you get the details of the account(after buying it) you should change the email and password. By this nobody can change the password or email except admin.