And in California, if you don't have any employees, you may not be required to have workers' comp (but you should probably carry it anyway if your co-founder is not your spouse):
"My spouse and I are the sole owners of our business. We have no employees. Are we required to obtain workers' compensation coverage?
Generally, coverage for sole owners is optional. You would, however, need to have workers' compensation coverage for any employee you may hire, even if it's just one employee, and even if it’s just temporary employment."