Im fourteen years old and Ive always wanted to do ballet but havent had the chance to take any classes. Do you think that If I start now I can become a professional ballet dancer? What kind of exercises can I do in preporation for my ballet classes?Thanks

From what I hear, chances are not really good starting that late. I have friends that are in the ballet and they were finished with their training at 16 and 17 and dancing professionally. That is the age they seem to want new dancers. It takes years of training many hours a day everyday from the age of 7 and even then, many do not make it into the professional ranks. Maybe you should think about having the ballet training and going into contemporary dance after training. You can start much later for that. Good luck. I hope I haven't discouraged you. Just telling you what I know. I am not a dancer, but do have many friends who are.

Highly unlikely. Even with a perfect ballet body and facility you are really starting late. Unless you were born with 180 degree turnout, killer Achilles tendons, hyper-extended long legs, short torso, long neck with a small round head, feet with ultra high arches and a top bump plus great facility and get accepted into a great ballet academy to start training 20-30 hours a week (you would most likely have to be home schooled) with the best teachers, you may have a shot.
Just do it for fun. There are so few jobs and your competition will have started expert training at around 7 years of age in a major ballet academy. Even among them, very few make it.

Those people start to train very young, but there are no limits to your own potential. Check out a basic dance textbook from the library. It will have the basic positions, and basic excersices particular to dance and ballet.
Also, don't limit yourself to just ballet no matter how passionate. There are lots of dance studios that teach West Coast Swing, Latin/Ballroom, and Modern Jazz. My classes were not expensive $35-$50 dollars for 5 weeks.
Start to practice basic positions and excersizes until they become very natural, a part of you.

If you cannot takes lessons right now, check out dance instruction videos at the library. And, if you are serious, find a way to get into lessons. If there is a performing arts school in your city go and talk to them about a scholarship.