morrorj 98, I'm sure as a parent you've already learned not to leap headfirst into all the things our kids/grandkids get enthused about. Too often, the kid's enthusiasm quickly wanes when they find out there's some effort/study/etc. involved. Nevertheless, encouraging astronomy is an A Nr One Okay endeavor! You may even get the bug yourself. My life-long interest just recently came back to life and here I am pushing 80 and back into astronomy in a big way.
I go along with the other posters, check sites like Orion and see what you can get for four or five Ben Franklins. Really, a pretty nice scope which will open up a fantastic world for the entire family. I also recommend a Dobsonian (Newtonian Reflector) as a first scope and a strictly manual model; leave the fancy stuff for later which, in many cases, can be added as accessory kits. Dobs are easy to set up and use. Just be prepared to stay up late at night and also occasionally freeze your behind off if it's winter and you'll need lots of 'Off' at other times of the year. However, it IS worth it and opens up a whole new world. My best to you and your 13 YO....