This is the essay to read first, from a YC partner who co-founded Justin.tv/Twitch and has done equal splits across his own startups. It makes the honest case that early contributions are a tiny sliver of a 7 to 10 year build, so an equal split plus vesting protects the friendship better than haggling over who did more in month one. It is the clearest short answer to 'how do we split this without a fight later.'
Default to an equal split: the value is almost all in the years ahead, not in who wrote the first line of code, and a lopsided early split kills motivation when you need it most.
The real protection against a later fight is a 4 year vesting schedule with a 1 year cliff, so anyone who walks in year one leaves with nothing and the equity stays with whoever actually builds the company.
Have the awkward conversation now, on paper, rather than discovering the disagreement two years in when there is real value on the table.
