Safest way to buy claimed IG username?

Let’s say I want to buy an inactive IG username, and someone with the necessary access claims the username for me onto a blank IG account, and then gives me the password to that account along with the password to the linked email address.

Is this a safe way for the buyer to receive the username, or is there a way that the seller can somehow reclaim the IG account or email address? (e.g. if they do a password recovery of the email, if they report the email account as hacked, if they are still logged into the email account even after the buyer changes the password, etc…)