A big benefit of working for startups like Square is the opportunity for a non-linear upside. It would probably be more prudent to avoid working for startups,

A big benefit of working for startups like Square is the opportunity for a non-linear upside. It would probably be more prudent to avoid working for startups, if you are going to take this approach. This approach (taking money off the table as early as possible) will likely have a worse return than if you had worked for a traditional company which pays market rates using cash or cash equivalents.