It is still an option but: unless you start now you will have a hard time getting into professional ballet companies. It isn't too late to be a ballet teacher. If you want to go into contemporary dance, you are at the perfect age to start, any younger wouldn't have been much better. If you develop strong personality and stage presence with it, you shouldn't have too much problem (in comparison) in getting into a dance company. If you are more the Jazz or hip hop style, again, it isn't too late to start. The best hiphop dancer I've ever seen started somewhere aroung 18-19-20.
Expect, however, that you will only be a good dancer in ten years, though after six years you should probably have enough to start doing stuff. This shouldn't put you off, just think about having a job on the side or a double major in college untill you get good enough to do anything with it. Actually, when things get tough, just keep your eyes on the 10 year mark. It comes inevitably. Or so I was told by a contemporary dancer who went through some really hard times in his training.
As to the kind of program you should follow: even if you decide you want more of one style dancing than another, it is best to do a little bit of everything, contemporary will help you in ballet, and ballet will give you strength and precision faster than what most conceptial contemporary dance can give you. Both of these will be extremely helpfull in Jazz
And of course, the ideal is 3 hours of training a day on average untill you get to a professional teaching program. If you are really motivated and have a lot of potential but not enough time, perhaps 2 hours a day on average will do. (That is the amount I do. I started at 19 and 3 years later got accepted this year at a 4 year program for contemporary dance, but I painfully turned down the offer. Perhaps I'll go next year. I didn't however get accepted to two other schools I tried out for, I didn't have enough coordination, nor perfect enough pirouettes, nor enough years in Jazz.)