I'm 19; I don't have a full beard. No hair on chin. Will minoxidil help me & will there be any side effects?

Facial hair growth is a genetic trait.  If you have very little facial hair there isn't much you can do to increase the growth

You can ry minoxidil and see if it works for you.  Many young men want to accelerate their beard growth and ask
about it. It takes age (genetic triggers which occur in family lines) so
if you want to find out when your beard will grow out, you need to find out
when your father or grandfather started to grow theirbeard. Hormones should have kicked in nicely
by the time a man reaches 18 but he must wait out his genetics as
hormone alone are not responsible for the onset of beard grown. Beard
transplants can be done when the young man is a bit older (over 25) if the
beard has not grown in yet