You are not fully developed till 21-25 years old. Taking it with 16, is not a good recommandation. Remember, you can get some serious sides. This thing is no fun. How worse is your status? I startet going bald with 17 years old. I just used minoxidil, and till my 25 years birthday i got no mayor porblems with balding. Just last year, it kick in again. So there are allways some options.
I would definitely recommend exhausting all other alternatives until you are 18. At that point you can go to a Doctor and have them assess you getting on finasteride at the appropriate age