General overhead expenses are costs that involve running a business as a whole, whereas variable expenses apply to just one job. General overhead expenses include, but are not limited to office equipment, insurance, rent, vehicles, etc. Variable expenses apply to special insurance, waste removal, fees for permits, labor of employees, etc. Kramon, James. "Smart Business for Contractors." Money Matters: Pricing, Billing, Collecting, The Taunton Press, 2007, p.11. What is a Contract? What is the difference between a contract/agreement and estimates?