When buying any het. It comes down to do you trust the breeder, if they have a reputation as a trustful person then go for it. If they seem shady then stay away. Ask for a genetic guarantee and if they do not provide one, it could be a sign.* not all breeders provide genetic guarantees for hets(Garrick at royal constrictor designs) does not provide them, but he has a very positive reputation for providing quality hets that are true hets. And I have bought a het from him with no worries that he will prove out next year.
Remember the genetic guarantee is only as good as the breeders reputation.