I know you probably really want one, but why not wait until you can move out. What if she finds the snake? If she flushed your hamster I'd hate to think what she'd do to a snake. I personally do not think it's worth it nor is it responsible to risk it. Especially if you think you may be able to move out when you're 18 (you're already 17). I say think a little bit more about the safety of the animal and just wait. In the meantime just do a lot of research about snakes and find the right one for you. Or start saving up and buying a nice setup so that all you then have to do is move and add a snake. You also have to think about if wherever you move will allow the snake. Best of luck!