A zoning permit shall be required for an additional commercial vehicle to be parked or stored on a lot in a residential district. Such commercial vehicle shall be only allowed on lots of two or more acres. Said vehicle shall not exceed a gross vehicle weight of 20,000 pounds and shall be stored indoors or screened from view off premises, no closer than the dwelling or 100 feet from any street line, whichever is less, and 50 feet from any property line.