When you want to log in from different IP usually you need to confirm new IP through the mail and that's all... I play from different places, one IP from home, one at work, when I travel I have my laptop with me so new IP... I doubt that your account will get banned just because you changed IP! As I said, with new IP or a new device you will have to confirm that is really you and you can play!
So the only important risk is that when buying an account your mail address has to be changed on the site, or to buy an account with the mail! If not, you risk to buy it and the owner can take it back!
It can, and buying with accounts and need changed the mail seems a pain for me, if i'm a buyer, i won't buy something like that. Instead get the advantages from high roller account, what we get only a ban from admin because of account selling. Lol