I would really like to stress just how large these rabbits can get. You won't be able to make them a 'cage' per say. A potentially 20+ pound rabbit is just not going to fit comfortably in one. You're looking at putting them in their own room, with access to your entire house for the majority of the day. A dog crate would be a good 'base' of sorts, to put food dishes and hay and such, but I would never put them in anything that small for any amount of time.