I'm 19 with a similar hairline to you; you seem to be okay right now with your hairline. My advice would not be to use Rogaine. Finasteride works as a maintaining drug to keep your hair as it is, and then even thicken out some thinning hairs. All I can say is that you may experience one or two side effects if you do take finasteride, but then you could also get side effects if you use minoxidil. The only side-effects I've had from finasteride after a week of using it is a decrease in libido, which is now picking itself up again - in a month I'll be fine, and for the grand majority of people who do get side-effects will see them go after a month. Wait for your hair to get worse before you actually start taking decisive action though, right now it seems thick and full.