When I was 15 I was taking care of multiple reptiles also. Handling tarantulas, scorpions, snakes. Had a few turtles, frogs. I took great care of my stuff. But the big point I was trying to make was also that so much changes between the ages of 15 and 16.

When your 15 you cant work, when your 16 you can. You can mow lawns or whatever but you cant legally have a real job. Also, maybe he will want to start playing high school sports? Playing high school football takes 90% of your free time.... No lie. What else, maybe he will get a girlfriend, and become whipped? And lose interest in snakes and start to dig pie? Heck IDK but anything can happen between 15 and 16. It's a big deal to care for a snake that may live up to 30 years when your only 15.