Occupancy by caretakers shall be limited to occupancy by a single housekeeping unit, at least one (1) of whose members provides substantial services in the principal residence or on the subject property, and occupancy of the dwelling is provided by the owner of the property solely in exchange of such services. Such services may include repair and maintenance of the building and grounds, security services and personal services rendered to occupants of the principal residence, such as, the services of a chauffeur, domestic, social secretary, and the like.