While this is pretty good advice you also have to be prepared for your co-founder to act irrationally. I went through something similar many years ago. After a

While this is pretty good advice you also have to be prepared for your co-founder to act irrationally. I went through something similar many years ago. After a long discussion we decided to find a way for the company to buy back my shares and we'd part friends. Imagine my surprise when I came into the office the next day to find the locks had been changed and my co-founder was busy calling lawyers trying to figure out how he could screw me out of my shares. It doesn't hurt to have any legal, financial or other documentation pertaining to the company and your part in it that you may want, or need, set aside before these discussions begin. If things do get ugly you might end up spending a lot of time and money getting them later.