Ferry Pilot Collecting Payment After Flight is Completed

Has anyone had experience with ferry clients not wanting to pay either the rate or expenses after the flight has been completed? I am putting together plans for my first ferry. I am including an estimated cost breakdown including expenses for my personal travel and for the flight itself. I know there are a lot of dishonest and slimey people out there and am worried about collecting after completing the service. Has anyone had experience with this? What are some safeguards you use to ensure this doesn't happen?