No member of the Council or any officer or employee of the City shall have any financial interest, direct or indirect in any contract with or sale to the City of any materials, supplies or services, or any land or interest in land. A person who knowingly and willfully violates this section shall be guilty of malfeasance in office, and upon conviction thereof shall be removed from office. Any contract or agreement made in violation of this section shall be voidable at the election of the Council.