How can I cheaply travel from Louisville KY and return back to Chicago?

Me and my wife are going to school in Louisville and we would like to leave our car down there when we visit soon. This way, we only have to try to drive one car down there instead of trying to tow a car with the moving van. Towing would cost 100 dollars and be very stressful in not crashing the trailing car. Ive been looking at car rentals but all of them are at least 150 dollars for a one day one way rental. Anyone have any other ideas? The trip is from Louisville KY to Gurnee IL.