I once worked in a particularly good position where the owner (my boss) would repeatedly say something that stuck with me. He was proud of the fact that he had been able to 'hire people who are smarter than me'.
That got me looking at my co-workers in a different light, and indeed, there were several people who worked with me, and they were each better at something than the owner. I realized that by hiring this way, he got to take the credit for a remarkably well-oiled machine that was able to get all sorts of things done exceptionally well. We all did the impossible & it was because of each of our points of expertise worked in synergy- like a puzzle coming together.
So, based on this experience, I would wholeheartedly recommend that you find someone- doesn't have to be a co-founder, could just be an employee, to work on something where your own talents are 'less' (for lack of a better word). Someone full/part-time who's dedicated to business development I would imagine would be a valuable asset.
I learned from my own (failed) startup, that the unexpected is guaranteed to happen. And if you need to allot your time & attention to something else that suddenly comes up, it'll help to have that someone around to help bear the load.
-my 2 cents. Best of luck!