When you join a startup, you are trading potential salary (from a big company) for equity. That means you're making an investment, and you should ask all the no

When you join a startup, you are trading potential salary (from a big company) for equity. That means you're making an investment, and you should ask all the normal questions an investor would ask: what is the company vision, what's the background of the founders, has the team demonstrated an ability to execute, how big is the market, how does the startup shape up vs. it's competitors, what is the current funding situation, etc. On top of that, you still should ask all the questions you would of any employer: about the work, making sure you get along with the team, stuff like that.