Yep, the math definitely works out on the side of paying for food, water, and substrate over paying for each rat at the store. It also doesn't hurt that both my kids have volunteered to help take care of breeders and don't mind the fact that they're food. I think, as small as my collection is, one pair is probably all I need, and just keep the male and female separate until it's time to make more food. What I'm trying to work out, though, is whether it would be all right to keep the rats in the same room as the snakes. Common sense says put them elsewhere if I can, but it really is the easiest/best place for them in my house right now.