Guinea pigs need lots of space to run around in. You can choose to put your cage inside or outside. If you end up putting your cage outside read the chapter predators or dangers to keep your little piggies safe from predators. If you are planning on getting guinea pigs then you will need a cage fit for them. If you are going to get 2 guinea pigs you will need to have a cage fit for them. For example 47" by 24" or 53" by 34". If you want more details on cage sizes read chapter 4 "What You Need For Your Guinea pig cage". Most store bought cages are way to small so you should ether make your own CNC cage or diy wood cage or go online. A good online store would be Amazon.