If someone started ballet when 15, what are the chances of making it professionally?

I have never heard of anyone going professionally and starting at such an age, but anything is possible. It is very good that you have these characteristics because you wouldn't be able to do ballet or any type of dance without them. You will definitely have to work twice as hard and practice, practice, and more practice. Again anything is possible, and if you already have experience in different types of dance, this is also good.