One of my mentors once said to me, "It takes at least four or five years to see if a company is going to work. Generally more. If you're really fast, maybe you can get a sense of where things are going by the end of Year Three."
It's important to know that some problems lend themselves to for-profit solutions, and some lend themselves to non-profit solutions. The trick is balancing it so you can, to the extent possible, get the best of both worlds.