How am I not supposed to assume? If someone says they can't "afford" a $40 thermostat then that generally means there's no money for vet bills. If they said can't "justify" paying that, then that's different. I don't see a problem with a rheostat over a t-stat if someone chooses and it works. Just me personally, I prefer to use both at the same time. Rheostat set slight higher incase the tstat fails one day. I don't have alot of money, but I make sure my animals have the absolute best care possible.
As for backup sources to go to a vet, what if the parents or friends don't have the cash or your cards are filled with the unexpected car repairs you had to pay? I feel that since "you" are caring for a live animal, "you" should have the ability to take care of it at any time.
Just my opinion...