I think 14 years old is the cut off age if you want to go pro and you really need to put in the hours to even have a shot. I know some pro skaters that started at that age. Daewon Song, Chris Haslam. Ryan Decenzo, Neen Williams, Josh Hawkins, Terry Kennedy, Justin Eldridge and a lot of european pros.
Intersting enough, pros that started at 13 is a longer list, Jeremy Rogers, Kevin Romar and Marc Johnson just to name a few.
PRod started at 12, but thats not late I think.