The document provides advice for those considering joining a startup. It lists 3 reasons not to join a startup: you won't learn about business or have experience in many roles, you won't have control or ownership over decisions, and you won't be able to directly make things. However, joining the right startup with the right attitude can broaden, deepen, and strengthen your skills and experience. The document advises interns to carefully pick a sector and startup that matches their interests, and warns that while startups can be rewarding, they are also hard work and sometimes unrewarding. Overall, the document suggests joining a startup is good preparation and experience for eventually starting your own business.