Offering a 'Minimum Sales Guarantee' helps share the risk with the truck owners for smaller events or events without a history. Guaranteed minimums vary by truck and event, but generally are between $500 - $1,500. Events with guaranteed minimums will receive more interest from the trucks.
A 'Guaranteed Minimum' simply means that if sales fall short of the agreed upon amount, you are responsible to make up the difference. (Agreed amount - event sales = amount you owe.) If event sales reach or exceed the guaranteed minimum, you owe nothing additional.