This document provides guidance on starting an online marketplace. It discusses Udemy, an online marketplace for courses with millions of students and thousands of courses. The vision is to let anyone learn anything online. Key aspects of building a successful marketplace include technology, community, brand, operations, and network effects. The document discusses designing the marketplace, centralization vs decentralization, getting initial traction through early supply and demand, focusing on segments, and leveraging success stories and third party channels for early growth.