Need advice on getting a pet fish for son?

If you want to keep the fish for a while I would not recommend putting it in a regular fish bowl. Instead get a small tank with a filter. You will need to chane the water and make sure ut has the right pH. You can get supplies at any pet store. Also during the winter it might need to be heated. This all sounds complicated but if you want the fish to have a long life then this is what you do. I have had my fish for 6 years now. Good luck!!