Any person engaged in the business of mechanical contracting shall register with the city prior to doing any work within the city. The fee to be paid to the city for such registration shall be one hundred dollars ($100.00) for a contractor, ten dollars ($10.00) for each journeyman and five dollars ($5.00) for each helper. Such registration shall be for a period running from August 1 through July 31, or any part thereof. (1993 Code § 5-108)