You want to hire someone who has "drank the Kool-Aid". You will want to look for people who are not risk-averse. Those who see benefits in building something from the ground up. That is part of their reward. They thrive in an environment where risk is part of the game. They may have a little entrepreneur in them also, but never could take the leap all on their own. If you hire people like that, you will feed off of each other. If you hire properly, your company truly becomes greater than a sum of its parts.
When you interview, pay attention to the questions they ask. Let them speak and ask the questions. You will learn more in the interview process if you let them drive it. You can learn much more about who a person is from the questions they ask, than any answer they will ever give. If you ask the questions, they will tell you what they think you want to hear. True character comes out in questions. Not to mention the fact that if you are founding a startup, you think your product or service is the greatest thing that ever existed. You should, or you will never succeed. But part of that is, if you do the talking you will spend all the time trying to sell them on working for you, and you will never find out if they should.
If at anytime they ask questions about vacation time, PTO, working hours, insurance or benefits, it is quite likely they are not the type of person that a startup needs. If they ask about stock options, profit sharing or IPO's, you might have a winner.
I also would advise you to hire slowly and fire quickly. With a few exceptions, I will freely admit that every person I have ever fired, was someone that I should have never hired in the first place. It was my fault, not theirs. They can be the most skilled person in the world, but if they do not fit with your vision, dreams, goals and culture, they will be a boat anchor you will have to cut loose. You cannot afford that right now.