A word of warning about choosing to start a startup: It sucks! One of the most consistent pieces of feedback we get from YC founders is it’s harder than they could have ever imagined, because they didn’t have a framework for the sort of work and intensity a startup entails. Joining an early-stage startup that’s on a rocketship trajectory is usually a much better financial deal.
On the other hand, starting a startup is not in fact very risky to your career—if you’re really good at technology, there will be job opportunities if you fail. Most people are very bad at evaluating risk. I personally think the riskier option is having an idea or project you’re really passionate about and working at a safe, easy, unfulfilling job instead.
To have a successful startup, you need: a great idea (including a great market), a great team, a great product, and great execution.