I am someone exactly like you. I am 17, and big in web development. The thing that incentivizes me is 2 things:

1) Being able to finish, and then continue the business aspect of it.

2) see if the idea was really a good one. This will be measured by its popularity.

3) If all others fail, just to have something to put on your resume.

What I do is I take ideas, and just run with them. People who wait until they get this "golden" idea, will end up doing nothing.