A recreational vehicle dealer licensed to sell recreational vehicles may operate one (1) additional business at the recreational vehicle dealer's established place of business; provided, at least sixty-six percent (66%) of the recreational vehicle dealer's established place of business is used for the sale or service, or both, of recreational vehicles and that the income derived from the additional business is less than thirty-three percent (33%) of the gross income of the dealership. The recreational vehicle dealer may also install signs at the dealer's established place of business for the purpose of advertising the other business.