I am 14 and have a (rescued) Russian tortoise. I got him just about a week ago, but did extensive research before hand. He has enough space, enough variety of food, and I am currently treating him for MBD, and he's improved so much health wise over this last week! We also have a plan that once I move out he will live with my aunt until I am able to bring him back into my home. So in my opinion if the teen/child and their family do extensive research and have a plan for when that child moves out and is establishing their adult life, then I would think it's okay.