The only way I can think of are airdrops and testnet which are very popular now but he will never own those wallets he can use them to claim of course he will not tell us where to claim and how to claim, because he is just the second owner, the only risk is if the former owners can trace where he is using the wallet he sold and beat him to claim it, I hope it's worth the price.
First time I've seen an offer to buy an old address, when in fact you cannot really own it.