Im 18 and im on monoxidil so ill tell you my results.
It just speeds up the length growth process for me but i dont see really any bald area's with any new hair,maybe 10-25% a difference but thats all.
Monoxidil caused slight headaches and a little bit of diziness for me but it was ok, it also made my heart go faster so its not for people who have heart problems.
Also if you get a little bit of monoxidil on your face beware because it hair can grow on those places.