For me, it was after only a few months of training. But I started off 60lbs over wieght, and weak as hell. So dropping 40lbs and increasing my strength by 25% in 4 months was dramatic, and fairly easy. It depends on what you have to work with really. If you have a high metabolism and are trying to pack on lean body mass then it may take a year or more to really see a difference in the mirror.
I don't do this for my family, my friends, women, accolades, pride, or ego. I do it for me and no one else, its just part of who I am.