It's not safe, no matter what circumstances under purchasing account are the original owner can recover the account with the adequate details. If the seller isn't the original owner, he/she can still recover the account or cause the account to become locked as their IP address has been registered under the account for longer period of time than the buyers will have been. I would highly suggest advising your friend not to buy the account either because you have no detailed analysis of the seller e.g. vouches. If your friend is looking for a secure account, the safest option would be purchasing an account from a trusted member of this community e.g. N4no's account shop. He guarantees a refund if the account is recovered and there isn't a short probation period where he washes his hands after 'X' amount of days either.