What procedure does the Milwaukee Police Department or Shiriff's Department use for determining whether a vehicle should be towed, impounded, or moved?

I heard there's two procedures: one for vehicles parked on private property and one for vehicles parked on city or state roads.

Any information on the procedures could be valuable to me. This is in effect I'm establishing a towing and storage business unlike any other. Its customers will be people recently incarcerated, booked in jail. It could be described as a private vehicle impound service. The terms include 90 days to pay in full whereas the authorities include 30 days.

Any information regarding towing vehicles would be very appreciated.