Your piggy litter will be smaller than with mice or rats, probably only about four animals. Guinea pigs are born fully formed, with hair and with their eyes open. They will eat regular food from the first day (strictly herbavore). They cannot eat corn or avocados, both are poisonous to them. Also, they cannot make vitamin C in their bodies (like ourselves in that respect), so they need Guinea Pig food, and not rabbit pellets or gerbil food. And yes, you can eat them, although it's not the custom in Canada. They make great pets (as do rats, as mentioned), much nicer than gerbils or hamsters.