A few years back, the federal trade commission (FTC) published a pamphlet to assist homeowners in selecting a reputable contractor to perform work on their home. In part, it was to inform them of scams out there that were victimizing unsuspecting people. It is filled with useful information that I highly recommend reviewing prior to engaging a contractor. I found it so helpful that I gave a copy to my mom to help her manage a commercial property that she owned. Here is a link to the website on which the pamphlet is based: http://www.consumer.ftc.gov/articles/0242-hiring-contractor