Professional office. For purposes of this section, professional office shall specifically be defined as offices where services that require specialized training, professional certification or an educational degree beyond a baccalaureate degree are offered by a professional including but not limited to accountant, appraiser, attorney, architect, landscape architect, engineer, surveyor, physician, dentist, chiropractor, optometrist, psychologist and similar professions. No goods or merchandise shall be offered for sale or exchanged within or without the professional office. The minimum lot size shall be 20,000 square feet.