My brother is a former Force Recon (Marine Corps) and is starting a private security business. He is a good guy, but can barely add past his fingers, so I'm trying to help him. A typical job for him involves providing security for a nightclub. I have several questions: 1. What is the average profit margin in the business? For example, if he incurs $100 of cost on a job, what should the markup be? 2. When estimating costs for a job, by what percentage should it be increased to cover unanticipated cost overruns? 3. Can you give me any other advice or tips for him?