It's important to determine whether or not the person is qualified and capable. While questions have their merit I'd recommend a more creative exercise.
If you have the means, take a trip half-way across the world and live in close quarters for 3 weeks together (while you work to get the business off the ground). If you can't stand them by the end of the trip; walk away.
I've been working with my cofounder for 15 years now and together we've accrued more than ~$30M in combined revenue from a handful of projects. Being able to argue, disagree, make a decision, move on and then grab a beer after work like nothing happened is paramount. Your personal relationship with this person will be the first domino in every decision you make.
If you have the means, take a trip half-way across the world and live in close quarters for 3 weeks together (while you work to get the business off the ground). If you can't stand them by the end of the trip; walk away.
I've been working with my cofounder for 15 years now and together we've accrued more than ~$30M in combined revenue from a handful of projects. Being able to argue, disagree, make a decision, move on and then grab a beer after work like nothing happened is paramount. Your personal relationship with this person will be the first domino in every decision you make.