Each scientist, naturopath, or chiropodist practicing his profession shall pay an annual license tax of $10 to the state, but no license tax shall be paid to the county. If such business is conducted as a firm or corporation in which more than one person is engaged, each scientist, naturopath, or chiropodist so engaged shall pay a license tax of $10; provided further, that no scientist, naturopath or chiropodist shall be required to pay a license tax until after he has practiced his profession for two years.