Well like the OP i also hope to have a career in photography, and as a 17 year old I can already see that it will be a hard profession to get into. But in a strange way, that is what i like about it, as we all know that anyone can pick up a camera these days and get some decent pictures, and that fact alone makes me think about what i can do to be a cut above the rest. The saying that comes to mind about this career is "Without challenge there is no achievement". I know that i have a long way to go before i feel that I can make a career, but it is a goal that I have set.
Anyway, the only piece of advice that i can give to you is ask around. I know this works from personal experience (yes a 17 year old with a tiny bit of experience!) when i contacted my local football club. As it turned out, their photographer had gone walkies, so needed someone to take photographs for them. I have only done this for a few games at the end of last season, and the junior presentation evenings, but now i can look forward to a season of football photography - which is what I want. So the moral here is - There is no harm in asking. Who knows, it might be the start of your career.
Anyway, good luck with it, and just listen to the advice of the more experienced users here, as i am no expert lol.