You need to sign a shareholders' agreement, addressing the following topics:
1. Minimum # of hours each founder is required to work each week.
2. Overall duties each founder will perform.
3. # of shares each founder gets.
4. Vesting schedule for each founder (tied to the # of hours worked).
5. Side projects, if any, each founder can undertake, including any boards each founder can sit on.
6. How much each founder can spend without approval from the other founders.
7. What level of hire each founder can make without approval from the other founders.
8. Under what circumstances a founder may be terminated from the organization.
And many more issues so as to avoid as many misunderstandings as possible in the future.