(b) Persons engaged in the sale and installation of a modular dwelling shall pay the tax imposed by this article on only the value of the materials used in the manufacture and installation of the modular dwelling and the preparation of the site for permanent installation and not on the labor involved in such activities. For purposes of this section, the value of the materials used in the manufacture of the modular dwelling shall be the actual cost of the materials and building supplies to the manufacturer as delineated on the invoice to the purchaser. If the actual cost of the materials is not available, then the cost of the materials used in the manufacture of the modular dwelling shall be sixty percent of the total cost of the modular dwelling. A credit will be given to the purchaser for any sales or use tax that has been lawfully imposed by another state and paid by the manufacturer on the purchase of building supplies and materials used in the manufacture of the modular dwelling. If the manufacturer pays the tax at the time of purchase of the building supplies and materials, the manufacturer is responsible for maintaining records evidencing payment of the tax and delineating the amount on the invoice. Failure to maintain such records will result in the credit being denied.
(c) Definition of modular dwelling. -- For purposes of this article, a modular dwelling shall include, but not be limited to, single and multi-family houses, apartment units and commercial dwellings comprised of two or more sections without a permanent chassis, built to a state or model code other than the National Manufactured Housing Construction and Safety Standards Act of 1974, which are primarily constructed at a location other than the permanent site at which they are to be finally assembled and which are shipped to the site with most permanent components in place.