Stylistic differences

Before partnering up with a cofounder its worth finding out what their negotiation style is like.

Is it adversarial?

Is it manipulative?

Is it logical?

Is it strategic?

Worse, is is sulky, sullen and angry (a form of manipulation) until you acquiesce?

A lot of your cofounder’s negotiation style will stem from their home life, so it is worth looking there as much as asking questions.