[pcpcpc]

I'd also ask questions to get a sense of the "soft skills" of the founders or whoever will be managing you. It's a truism, but "people quit managers, not companies."

There are tons of resources online for questions to ask, and I think the company/viability questions from the post are good, but I would add to them some of these types of questions:

How you will be managed/evaluated and the mission of the company: https://www.themuse.com/advice/8-questions-most-people-dont-...

How your founder/manager will navigate conflict, which is inevitable: https://www.thebalancecareers.com/interview-questions-to-ass...