Sec. 5. The expenses and obligations of the district may also be paid from any of the following:
(1) The receipt of gifts from any source.
(2) The receipt of money from the federal or state government.
(3) The receipt of revenue from the sale of services or property produced incident to the accomplishment of a purpose for which the district is established.
(4) The collection of assessments from land that receives exceptional benefits from the operation of the district plan.
(5) The collection of assessments for maintenance and operation of the works of improvement.