With no paperwork and only the word of a possible het I would just consider him a normal. You could also try contacting a herp rescue or group if any are near you, maybe they would know a breeder or experienced home they could recommend rehoming it to. If you are placing an ad I guess it's hard to say, I wouldn't want to risk full price on a snake that may not eat if I were looking to buy but you do run the risk of impulse buyers if you go too cheap. Ask questions, it's not too hard to figure out if someone is fairly knowledgeable on snakes. As for selling the snake minus cage, if it's just your basic aquarium setup anyone in herps should be able to set one up fairly easily, most reptiles I see for sale are minus setup. Or include a setup I wouldn't want.