More startups die from co-founder breakups than from competitor moves. The agreement you sign before there's anything to fight over is the cheapest insurance you'll ever buy.
The most common. Removes ego from day one but creates deadlock risk. Mitigation: assign tie-breaker authority to one founder for specific domains (CEO breaks ties on commercial; CTO breaks ties on product/eng).
Equity split adjusts based on time and capital contributed. Powerful pre-incorporation; messy post-incorporation. Best for the first 6 months while you're figuring out the team.
Sit down for 4 hours and walk through: who has the idea, who quit their job, who's putting in capital, who has irreplaceable skills, who has prior network. Score on each, weight by importance, calculate. Awkward but durable.
4-year vesting, 1-year cliff, monthly thereafter. If a co-founder leaves in month 11, they get nothing. Month 13, they get 25%. Investors will require this anyway — better to set it yourself before they ask.
Apply vesting to all founder shares, including the ones you "already own". Yes, you're vesting your own equity. That's the point.
Every founder, contractor, and employee signs an IP assignment from day one. Without it, the code your friend wrote on a weekend "to help" still belongs to your friend. We've seen rounds collapse in DD over a missing assignment from a 2019 contractor who's now uncontactable.
Write down — actually on paper — who decides what:
The hardest conversation. What happens if a co-founder wants to leave, or needs to be asked to leave?
Before signing legal docs, do this exercise: each founder writes down separately what they expect of the others on (a) hours worked per week, (b) responsiveness on weekends, (c) salary expectations year 1 / year 2, (d) exit timeline. Compare. The gaps are where your future fights will be.