Go used. eBay is actually a decent place to find gear, but you need to know what to look for. It's easy for me because I favor rod actions from the late 80's. They might be a half ounce heavier than today's best, but I still contend they're better to learn with. What do you intend to fish for, and where? How old is your son (I'm too lazy to scroll up). No reason you can't gear up for $250 for rod/reel/line.
My son is 14. To get started in the sport, we would primarily be fishing southeast PA streams for trout and small mouth bass. I'd like to get up to central PA or the Poconos this summer for a little better fishing than what we have here. As I understand it, our local streams get a bite warm in the sumner. Who knows where it's would go from there.