how long will it take until i can be able to work for security?

i wonder if me not having my high school deploma will effect me getting in my trade/security and im also wondering about my well being because im to young to carry a weapon . will I have to wait till im 21 to carry one? or will i be doing something else in security until i be 21. i heard i have to be 18 for a state id for the security.