Paul,
They need to be able to transverse their cage, and thermoregulate their body heat. I put a heat pad at one end usually the bottom. That way they have both a warm spot and a cool spot. Experts say not to use a heat rock, they may burn themselves. As for housing two in a cage, I have known it to work, but you may subject one or both to stress and they will stop eating. I find it not a good idea.... . As for substrate, a controversy can exist, but I use aspen, and avoid the others. Some people use just plain paper, with the idea they won't ingest fibers when it is feeding time. As for lighting, my understanding is they don't have to have UV. Hope this proves helpful. I think a lot of this is on older forums which have previously been posted. Steve