8. Valuation/contracts.
Decide on a formula to determine the value of the company should one partner decide to leave to avoid disagreements. Buy/Sell agreements are incredibly useful for discussing all possibilities and how they will be handled before they become a reality.
Why is all of this so important? Because a great business can be severely damaged by a bad partnership and never reach its full potential. Starting a business and/or a partnership is an emotional experience. When doing your due diligence, set your emotions aside and make sure everything lines up and has the potential at staying aligned.