You have to be skillful
To become an NBA player, the only rule is that you must be at least 19 years old or play one year in college.
It does not matter how old you are. if you were good enough, you could be 10 years old and play in the nba. Lebron James and Dwight howard were drafted out of high school.
NBA player Kent Bazemore played for Old Dominion.
In order to play in the NBA you must at least play one year in college. So you pretty much have to be 18 or 19 unless you skipped a grade.