I wonder how much work is actually involved with running such businesses that cater to peer economies. Airbnb, Uber, and Lyft, their site is a simple web app. I see more and more startups with simple web apps that is catered around a business model that involves being a marketplace or automating some process.

What's happening behind the scenes to such startups? Is it a group of marketers?

Say I create an Airbnb clone, what now? Or say I create Uber app, what's the next step? Does the chicken or the egg come first?