Getting into commercial inspections

How does one get started in commercial inspections? Before I became a home inspector I worked for a company that built commercial and residential buildings, but I would in no way say that I was ready to inspect commercial property as I know it is completely different. I guess the questions I have are; where is the best place to get training, how did most of you market your services, is the cost of getting started doing these type of inspections worth it in the long run, and is liability any greater than regular home inspections? Any information you might have would help me out.