Registration and Liability insurance wouldn't be too much. Put a locking deck lid on it and fab up some tail pipes or throw a junk engine in there.
The only difficult part would be emissions without an engine... or you could put an electric motor in it and it would pass!
As for using it for the business...yeah... its a sign!
Or you could always do the old mount a vehicle on a large post! Perhaps if it "has a foundation" its no longer a "vehicle"

according to the sign ordinance it says:
"Any sign painted on or attached to a vehicle and used as a stationary sign."(chapter 3-21-a-5) So if its a mobile sign.....
But then Chapter 3-21-c says:
"For the purposes of this Section, a rebuttable presumption shall arise that a vehicle is being used as a stationary sign if (1) any sign is painted on or attached to the vehicle, (2) such vehicle is not titled or does not have a license tag affixed thereto, and (3) such vehicle is located in a front yard (as defined in the Chattanooga Zoning Ordinance), provided that no such presumption shall arise with respect to trailers which are used in the ordinary course of business in a trucking operation."I say we take that former "RV" and get you a tax break on your "second residence"
its all about the loop holes!!! or the a-holes...