I like that you have done your research, very admirable, especially at your age.
However, it is HER house, you are HER child and until you have your own place you need to abide by HER rules.
You mentioned that you would probably be moving out sooner than later. That, combined with the life-span of a BP means it shouldn't be that hard to wait few years (ok, truth be told, I'd be anxious to get one too) until you do have your own place.
Something to consider in the meantime: I don't know your college plans, or your moving out plans or anything, but there are a LOT of places that wouldn't allow you to keep a snake there. College dorms, most apartments near colleges, and plenty of apartments and rental properties will not allow pets, exotic pets or even snakes specifically.
I had to rehome snakes when I was younger and had to move back in with my Dad for a bit. It was tough, but my options were extremely limited.
I think it's worth the wait. You seem like you'll be a great snake keeper when the time is right. If it's something you still want in a few years when you can home the snake yourself, then by all means go for it. Until then, you need to abide by and respect your mother's rules.