Your going to need a decent sized cage. Personally, I would go to petsmart and shop around just to get an idea NOT buy mind you. Their prices are ridiculous. When I kept 2 rats as pets before I figured out that Kingsnakes who constantly smell rats are not the greatest pets, I kept them in a decent sized plastic tub with a 2 levels/perches glued onto the sides. Increases floor space quite a bit and they do love to climb and look at you. I don't know the size seeing as it was a while ago but I would think that anything 2.5-3 feet long plus around 2 feet in height should work well. Get creative!