A buyer and I were discussing a possible partnership with the selling business owner.  Because I am neither an accountant nor an attorney, I always demure from making structure recommendations but I certainly have opinion on things that should be included.  This is a quick list made for the buyer.   Perhaps you have other contributions.

Quick notes:  These are things that I believe should always be in place in a partnership:
An operating agreement that makes clear who is responsible for what, how they are compensated and under what conditions can they no longer be responsible, under what conditions investments and owner payouts are made.  If money is required for investments, debts, etc who is required to put in money.  Does there need to be agreement on company direction?
How to get out – including death of a partner, partnership not working, owner wanting to buy or sell share – price, to whom, timing, and agreed to timing and conditions for total sale – to other than owner.  Does the company buy a life policy to cover circumstances.  Can an owner not be working the business?