I manage a C421 and I charge $750 per mo for my time. I also fly the aircraft @ $300 per day. Additionally, I get a piece of the acquisition cost (usually a flat fee of $5K) and the selling price (2-4%). The company then depends on me to crew the aircraft, maintain, charts, etc. A complete chart subscription is kept on board and headsets are paid for by the owners.
Hope this helps.
Flydaddy0499