Having built a product, I'll also add that early on it's not just about finding someone you can work well with, they also need to believe in the product and bring some level of passion for it to the table.

I can work well with any number of people, but few understand the importance of things like audience building, using the product on a daily basis, etc., and even the ones that do might not act on that stuff. Overall passion for execution and moving the product forward are critical.

Maybe this is what you meant, but I wanted to add my 2 cents to clarify.