Business partnerships rarely fail over the idea. They fail over things nobody wrote down while everyone still got along.
Who owns what
Shareholdings, and what happens to them if someone leaves, stops contributing or dies.
Who decides what
Which decisions need unanimity, which need a simple majority, and who signs what.
Money out
Salaries, drawings and dividend policy, agreed before there is anything to argue about.
The exit
A valuation method and a buy-out mechanism, written when both of you are being reasonable.
