I will point out the obvious and say make sure they are a state licensed contractor with no bad reports on their record. Go to
http://tn.gov/commerce/boards/contractors/ and click on the license search link, then click the link at the top of that page, enter the search parameters (put in zipcode and in the drop down box click on contractors) to find licensed contractors in that zipcode. Active fully licensed is the what you are looking for. Click on the details button to get license information. The classification you are looking for is "BC: A". The BC stands for a building contractor (I assume) and the "A" denotes a residential contractor. They may have more than just an "A" but as long as they have that and their monetary limit matches or is more than your house will be, they are able ( by state regs) to do a custom build for you.
May not be info you were searching for but that is the best I can offer from west tn. One other thing a house built "to code" is a min standard only. It does not guarantee the highest quality construction.
Do any of you fine folks know of a good, honest, reliable home builder in the Crossville area. Any info would be greatly appreciated.