Subject to and consistent with the percentage of financial participation determined by the board and approved by the electors of the region, as provided in sections 21-804 and 21-805, Idaho Code, or as determined by the board as provided in section 21-807(14), Idaho Code, an authority may secure the necessary funds to finance part or all of the cost of acquiring, establishing, constructing, developing, expanding, extending or further improving the regional airport within its limits through the issuance of general obligation bonds as hereinafter provided, the principal amount of which at any one (1) time outstanding, shall not exceed six-tenths percent (.6%) of market value for assessment purposes of all property within the participating counties within the region. Provided further, all such bonds shall be payable within thirty (30) years from the date of issuance.