I encourage you to go after your passion, and see how far you can go. Even if you do not meet your goal, your life will be greatly enriched by ballet and you will know that you gave it your all. No regrets! Given all that, you must be prepared to make sacrifices both financially and in the amount of time it takes to go to class. Also you must be aware that the pre-professional ballet world is geared toward and designed for teens. You may find a small company that you can dance with as an older adult (in dance terms!), but you must realize that you will probably never be hired by or get to the level of a major company.
I fell in love with ballet at 19 years old, a sophomore in college. I studied dance intensively for 3 years (I'm 22 now) and I got further than i think anyone ever expected me to. I was even able to attend a summer intensive, dancing with 14 year olds, at a respected company after my 2nd year of study. To get to this level, it took a *lot* of commitment. I danced and trained 9 hours a week at my peak on top of a full load of classes at school. If I ever hoped to get to a professional level, however, i would have to continue at this level for many more years! As i progressed, however, my goals changed. I no longer have apsirations of dancing professionally, but I will never regret putting my energy into studying dance. I learned a lot about the art and about myself in the process. I never forsee letting go of dance, however, and there are a lot of was that I can use my training in the future.
In my view, you have nothing to lose in giving it a shot, as long as you look at it realistically and rationally. Good luck!