Starting a business with a partner or team is exciting, but without a clear founders' agreement, you are building on a shaky foundation. A founders' agreement — sometimes called a co-founder vesting agreement — defines each founder's role, equity split, vesting schedule, intellectual property ownership, and what happens if someone leaves or wants to sell their shares. William Green explains why this document is essential from day one, drawing on real cases where missing founders' agreements led to company-ending disputes. This article covers the key provisions every founders' agreement should include: equity distribution and vesting, roles and responsibilities, decision-making processes, IP assignment, non-compete and confidentiality obligations, and dispute resolution mechanisms. Getting these terms in writing before tensions arise can save your company — and your friendships.