Investigate licensed contractors before you hire them
If a contractor knocks on your door, or leaves an advertisement in your driveway or on your door, it's very important that you investigate them before you sign a contract or hand over any money. The Arizona Registrar of Contractors maintains a website where you can find the status of any licensed contractor in the state. In order to be licensed, the contractor must post a $200,000 deposit or bond in a recovery fund that was established in 1931, when the Registrar's office was created.
If the builder or contractor is licensed, the status of its operating permit will be displayed as well as contact information, and their license number (which should be included in all contracts). A listing of complaints (both resolved and unresolved) will be shown. But the big thing to remember, if there is no license for the contractor shown; run away as fast as you can!