If you're looking for ways to attract buyers, consider offering a warranty for the first year after the sale. The assurance that they won't face major repair bills right away may make some buyers more comfortable with your asking price.
Make sure the compressor’s output matches the pounds-per-square-inch requirements of the tool to be used. Check and change the oil regularly. After a day of use, empty the air tanks and drain any water build-up inside the tank through the drain tap at the bottom of the tank.