Except as otherwise provided in this Act, it is unlawful for any member, officer, employee or other appointee of the Board and District or for the husband, wife or minor child thereof to have, acquire, obtain or hold any contract, work or business of the District, whether for stationery, printing, paper, services, material or supplies, or any private financial interest in the sale or lease of property to or from the District. It is unlawful for any firm, partnership, association or corporation from which any such person shall be entitled, by contract, stock ownership or otherwise, to receive more than 7-1/2% of the total distributable net income thereof to have, acquire, obtain or hold any such contract, work or business or any such private financial interest. It is unlawful for any firm, partnership, association or corporation from which any such person, together with his or her wife or husband or minor child or children, or any of them, who shall by contract, stock ownership or otherwise be entitled to receive in the aggregate, more than 15% of the total distributable income thereof to have, acquire, obtain or hold any such contract, work or business or any such private financial interest. Any person, firm, partnership, association or corporation which violates the provisions of this Section shall forfeit any and all sums paid or to be paid to him or it or her by the District under any such contract, sale or lease and, if found guilty of such violation, shall be guilty of a business offense and shall be fined not to exceed $2,500.