I have found a potential cofounder. Both of us would like to work together for a trial period. The goal is to test out our work compatibility and team dynamics. What is a well-recommended test period? What kind of agreements are common for such a test period? How should the work done by each of us during this period be valued (compensated) before formally becoming cofounders?
21 July 2020:
A few more details:
You could put together a contract similar to a "typical" cofounder's agreement, with equity-only as compensation and short-term vesting schedule. Will there be a "controlling" Founder? (Meaning is one of you going to hold more Founder's equity than the other). This is an important distinction to allow good answers to follow.
The first step is to figure out how you're going to measure "success" of your working relationship before anything else. Second, is why a co-founder? Do you both have identical vision for the company and identical goals? If you don't, then you're not co-founder material. You may have found your first employee though. Co-founder doesn't inherently mean "willing to work for equity only." It specifically means that you share a unified vision and goals. Your first employee might not be compensated with a salary, but it does not make them a co-founder.
What you're describing to me initially is that you have an early employee, not a co-founder.