A good breeder should let you check out any snake you are thinking of buying and offer contact info. I haven't seen many offer any kind of warranty. Don't be shy about looking at a lot of different animals. It's your money and you have a right to inspect what you are buying.

But yeah, don't expect a warranty but do get their contact info in case you have questions about it's usual diet or what not. And if you are buying a het try and get paper work.

Hets are always a gamble so make sure you trust who you are buying it from.