One of the biggest things to consider is how healthy the animals look at the pet store. If you're not sure, watch the animals at the pet store, and make an appointment with your other sources that you might adopt a pet from. Even if the pet you want to buy does not look sick or hurt, if the other ones do, it's not a good idea to buy from that source. I watch when I buy fish. I watch for fish that are dead in any of the tanks at the pet store. I watch for sick fish. If the person or store you are purchasing from is not removing any sick or dead animals from the rest of the animals, it is a problem. You watch the animal really close those first few days, and if it looks like it might be getting sick, you take it back. Don't purchase an animal from a source that won't give you an exchange within a reasonable amount of time. I know it's hard, but try not to get too attached at first.