I think most of us have been in that position...some have tried for the save, some don't (for a whole bunch of reasons). Many will tell you that to take this snake home is asking for trouble (myself included , but I've done it). If it is as bad as you say, chances are you will not save it...but you could endanger other snakes in your collection by bringing it home. If you are not concerned about that, and want to try - ask to speak with the manager that oversees the animals. Show him/her the snake & express your concerns. Offer to explain proper care of this snake to the person responsible for it. Depending on the responses you get, you may want to make an offer (remember, they get these things CHEAP and it is in bad shape). Not knowing how big it is, how bad off it is, (what morph it is), the asking price, etc, it is hard to recommend a figure...but since you are saying "thin as a pencil" like it is bad, I'm guessing at least a yearling. IF after really looking it over, you think it is salvagable, offer them 1/3 their listed price (if they have it for $45-50, offer them $15), but be prepared to walk away. If you appear to eager too "save" it, they might try to hold out for $$. Above all, be realistic...if it's too far gone - save yourself some money and stress by walking away