Districts formed hereunder shall be exempt from all excise taxes of whatsoever kind or nature, and further, shall be exempt from payment of assessments in any general or special taxing district levied upon the property of said district, whether real, personal or mixed; such exemption shall include, but not be limited to, franchise taxes or assessments or fees levied by a county or municipality for inspections of the facilities of the district which were not requested by the district. Any and all securities and evidences of indebtedness issued by a district created pursuant to this act¹ and the income interest and capital gains thereon shall not be subject to the income tax laws of this state and persons owning or holding said securities and evidences of indebtedness or their heirs, devisees, successors, or assigns shall not be required to pay to the State of Oklahoma income tax upon the profits and capital gains upon said securities and evidences of indebtedness.