How old do you have to be to tryout for the AFL or the NFL?

i am going to try out...regaurdless...im not a quitter and its gonna take a miracle i know...but i believe...4.5 40 yd dash, bench 225 15reps...good high school film...im about 5'9-5'10 200 lbs...and very graceful and confident...plus the teams i seek to help out suck very bad lol