Also: obtain agreement on a few "what if" scenarios. For instance if you're at a foreign airfield and the plane says "no" somehow, because of a duff spark plug or some other relatively minor failure. That sort of maintenance, away from base, doesn't come as cheap as the same maintenance back at base. Who's going to pay for the overnight parking, hotel costs, the taxi & commercial flight back home and who's going to retrieve the plane eventually, once it's fixed?
When you rent a plane from a commercial outfit or not-for-profit club, this is the sort of thing that's normally covered in their terms of hire.
Because of this, a prudent owner will limit you to a certain geographic area where you can go without prior authorization. When you want to go further than that, you need permission on an ad-hoc basis.