Look up some info on the seller , Check the BOI.
All depends if you believe you can trust the seller, if the prices are decent for a possible het, and if your willing to take the risk.

50% hets are gambles and there is no guarantee that they are actual hets, you have to understand that if you bred them and got nothing but normal looking animals, you could have just missed the odds really bad or they aren't het at all.Neither of which would be the sellers fault since they were 50% possible hets to begin with.