S.C. Code § 56-3-710
For every house trailer the biennial fee is twelve dollars. The Department of Motor Vehicles shall classify as a "house trailer" every trailer or semitrailer which is designed, constructed, and equipped as a dwelling, living abode, or sleeping place, permanently or temporarily, and is equipped for use as a conveyance on streets or highways or a trailer or semitrailer of similar nature whose chassis and exterior shell is designed and constructed for use permanently or temporarily for advertising, sales, display, or promotion of merchandise or services or for another commercial purpose, except the transportation of property for hire or the transportation of property for distribution by a private carrier. The department may not license and register a house trailer which exceeds the permissible size limitations prescribed in Sections 56-5-4030, 56-5-4060, and 56-5-4070, but the house trailers permitted to be moved over the highways by the department under special permits issued pursuant to Sections 57-3-130 to 57-3-190 shall pay to the Department of Transportation a fee of five dollars a trip.
S.C. Code § 56-3-710