It's really ill-advised to solicit your vision from anyone. In my 20 years of building, investing and supporting tech companies, I don't know of a single success story that has it's origins in someone with your approach. Running a tech startup is incredibly hard. It demands sacrifices few are ...
The answer depends primarily on two factors: 1) Do you have outside investors? 2) Do you have and/or could you obtain a legal release from the co-founder, and after this release, would the co-founder have less than 5% of the company? If you have outside investors in the existing corp and you wi...