How does one get an investment for a web app?

I am nearing completion of a web app that is meant to be a data sharing and science-debating website. I suppose you could say it’s kind of like combing different aspects of google images, Quora, and Research Gate into one. I have a lot of visions for what features it will offer, but per people’s recommendations, I’ve opted to go try nail the implementation of just a few features that I believe will be the “bread and butter” of the app that people will find most useful. Then hopefully if it actually gains traction after launch, I could get an investment and hire developers to build the full version of the app.

I have a few questions:

1. Do any of you know anyone who has successfully implemented this approach?
2. What are the basics of even trying to get an investment in a web app idea?
3. How likely is it for an entrepreneur to get an investment for a web app idea?