I wouldn't get it just from your description. Someone that uses a heat rock is not someone I'd purchase an animal from-- it says to me that they haven't done an ounce of research on husbandry, because what would the point be if they already had a regulated heat mat?. There is a good chance it has burns.

If I were you, I would get an animal from a nice breeder so you can be almost certain that it will be free from health problems. Just my 2 cents.