I was a developer that partnered with a stranger. He's an MBA with a purely business background. I'm the full stack + product guy. I'm never co-founding a business with a stranger ever again.
We failed probably because of not what you're thinking. My business co-founder brought more to the table than I could imagine. I've gained a lot of respect for the hard work of sales, marketing, fundraising, and the people that make these tasks seem so easy.
We got hundreds of customers, made $10k revenue per month, and had a staff of 5 at one time. All bootstrapped over the course of 12 months.
The thing is, we were not happy working with each other. When shit hits the fan (which happens often in a new business), we just get on each other's nerves. On paper, we have perfectly complimentary skill set. He's a charming people person. I'm a proficient developer. In reality, the fact that we're so opposite means that we're always seeing and doings things differently. When we're in a grind, he wants to hi-fives to boost morale and I want to put my head down to ship faster.
If I were to do it again. I'd find a smart, hardworking person that brings me energy and that I'd bring them energy when the shit hits the fan. I wouldn't care if they're a CEO, CTO, C-whatever-O. I'd look for someone that I'd enjoy working with above all else.