It's been stated before, but it needs to be emphasized that account sales are extremely risky and if you're looking to buy an account, you need to have extremely high standards in the people you choose to buy from. Not just 20+ vouches, try 100+.
The reason owners can recover their accounts so easily is because the people they sell to have very different IP addresses from themselves. When they submit appeals to jagex, jagex recognizes their IP and gives it to them. You can use a VPN/proxy though to pretend that you live where the owner does, so it's harder for him to recover it and it's not as obvious that you're not the owner, but at the end of the day, he's gonna win any recovery war you get into