If you have to keep selling your idea, startup vision, and its future potential to retain the person during initial phase of startup, that person is not co-foun

If you have to keep selling your idea, startup vision, and its future potential to retain the person during initial phase of startup, that person is not co-founder. S/he is an early employee. Co-founders are the one's who have already bought into your vision and fully committed to and working toward the vision without any prodding, convincing, encouragement etc. They independently leading the effort and doing what need to be done to move the startup forward.