The age range for athletes has become younger and younger over the years, for one because your physical capabilities die down as you age and since being an athlete is a highly competitive job, people have had their kids start younger and younger. As a result, you have to reach higher standards in order to have a career as an athlete, therefore the sooner you start the better. I have no idea how old you are now but if you are in late teens or older, I'd suggest to even check before starting so you don't waste your life away at something that might leave you heartbroken. Having said that, age is NOT everything always, there are athletes that have tremendous talent and success even though they may have started later so you have to think of your own personal abilities, strength, stamina and how hard you are willing to work for it. Bear in mind that becoming a professional athlete requires a lot of sacrifices in life, are you willing to make those sacrifices?
I hope that helps