This is known as an operating agreement/ partnership agreement; in many states, new companies are required to make one by law. It states each partner's roles and contributions to the company, and how roles are divided. This details how decisions are made, where the capital investment or contributions come from (or how they will be sourced), the distribution of profit and salaries attached, where the partner roles will go to in the event of death or inability to perform duties, as well as the dissolution and exit strategies in the event the business needs to close.