I will go ahead and tell you don't do it.

Any snake you purchase is going to allow the pet store to replace it with two more to be treated exactly like the one you bought. They do not care for the quality of the animal or the quality of its life. They only care for the bottom line. I hate to sound cruel, but the only way to stop a pet store from selling an animal is for the pet store to be unable to sell it.

If they have to eat the cost, they won't replace it. It is better in the long run to let an individual animal die in their care than it would be to "Save" just that one animal.

Instead, if you buy directly from a breeder you can trust, you are supporting the breeder who actually understands and cares for the animals and not the pet store who is just looking to get paid on the mark up.

Most of the time, you will find the breeder to have cheaper prices too.