Never ever ever EVER take non-science/engineer as co-founders. EVER. I'm actually inclined to say not to hire either until you're profitable. Unless it's necessary by evil, like lawyers. And by non-science, also include cultural science or political science.
I remember when we founded our first startup, it was three guys: the programmer (me), the business guy (a friend of mine), and our "account man" (an acquaintance of ours) - all equal shareholders. Shortly after founding, there was a discussion about having company cars. The two business guys wanted BMWs, and I was to get some cheap Japanese mini car. When I asked how they came to that idea, they explained that I was only the programmer and I could get by with basically nothing, whereas they insisted they needed BMWs for their role in the company. They also said, and I kid you not, that they were from wealthy families and I was not, so it seemed reasonable to them that everybody needed to keep their rightful place. Needless to say, I shot this down and shortly afterwards, the account guy left. It was for the best. Who knows what would have happened if I had let them get away with this.
Self-entitled, hypocritical, non-technical entrepreneurs. There are probably a lot of good people with non-technical qualifications out there, but it's easy to suddenly find yourself working with the bad ones.