I would add that the vision doesn't necessarily need to be the same, but a great co-founder can help improve your vision. I had a boss (and mentor really) who

I would add that the vision doesn't necessarily need to be the same, but a great co-founder can help improve your vision. I had a boss (and mentor really) who trusted me with the vision of the product I was working on, and in our early meetings, we would 'leap-frog' each other challenging the other to see a larger and larger vision.