Hey! - Totally understandable
Basically I want to participate in new incentivised testnets and they tend to reject wallets that are pretty recent as they think you might be a bot.
Which is why I'm looking for old wallets preferably with activity
Hope that clears things up

Selling of wallet really don't seem possible to me since even after the deal is done there is no full assurance of ownership transfer, the original owner can't always be keeping track of the wallet and might be tempted to move out your proposed funds which might be gotten from your said testnet