I think I did mention temperature in one of the sections. As far as housing, as long as they are getting a lot of out of cage time, a single level cage is fine for a ferret. Most single level cages have an insert that serves as a "second level" so the ferret can sleep away from his toilet. I have a Ferret Nation 142 model cage, which is a two level cage with mini levels on each of the main levels. This cage can house up to 5 ferrets as long as they are given sufficient out of cage play time, which mine do. I house four ferrets in it right now.