Everyone who wants to do a startup should thoroughly read and comprehend the Disco Elysium situation. This is why so much money goes to lawyers and why contracts should be written to have zero trust in your business partners even if you do have it.

Most people are fairly reasonable, but all it takes is something such as an unexpected divorce to completely unravel someone's decision-making to where they will suddenly be justifying any and all actions to take control and extract money for the good of their future self.