Wow, lots of questions! First of all, piggys are quite big but not as big as a rabbit. A hamster cage will not do, they need a big cage and a hamster cage would only just fit them, if you live in an appt. you may not have the space because indoor cages are so big they need to be on the floor so they may be in the way. I dont know how much they smell but since they are bigger than a hamster, I would guess the smell is more noticable. They do well in pairs but can be kept alone, in which case you would have to spend more time with them. I would say you need to do some more research if you dont even know how big they are. Hope I helped, good luck!