What characteristic is essential for a person to be considered a "used motor vehicle dealer"?

For a person to be classified as a “used motor vehicle dealer,” a key characteristic is the requirement to sell at least three used vehicles per calendar year. This criterion establishes a baseline activity level that distinguishes a dealer from individuals who may sell vehicles infrequently or casually. Selling three used vehicles demonstrates that the individual is engaged in the business of selling used cars, rather than just participating in occasional sales as a private seller. This minimum threshold helps to ensure that those in the industry are operating with a degree of continuity and professionalism, which is important for consumer protection and regulatory purposes.

The other options provided do not align with the established definition of a used motor vehicle dealer. For example, specificity to motorcycle sales, operating part-time, or being employed by a corporate dealership does not effectively describe the engagement required to meet the dealer classification. Therefore, the correct choice underscores the active role in vehicle sales necessary to be recognized as a used motor vehicle dealer.