You won't see visible results for awhile, most see visible results anywhere from 3 months up to a year.
However most people can start feeling differences with as early as two weeks, I think that you should start feeling differences within about two months if you are responding to it.
I started on March 17th, so I have no been on 0.25mg finasteride for 11 days.
So far I have noticed less greasy hair, and my scalp itch almost gone