Need a way to make Google Play account 100% safe when i sell it

Hello i am paying for a way to make the google play account ( Gmail account ) 100% safe once i sell it.

I will create/buy bulk google play/Gmail accounts and then i will play a game with it, after sometime i sell the account to customer X.

It should be possible that the customer can change the google play account details to their own or connect the google play account to their main account.

What we want to avoid is Mobile number verificatiion from the old device or anything that can lock…

Need a way to make Google Play account 100% safe when i sell it