Okla. Stat. tit. 82 § 1324.12
Plans, specifications, proposed operating budget, schedules of unit fees and benefit units, rules and regulations, estimates of cost for any proposed improvement authorized by this act shall be filed with the secretary of the district. The total benefits of any such improvement shall be divided into a suitable number of benefit units. Upon determining a schedule of benefit units and unit fees, the board of directors shall cause a declaration of availability of such units for subscription to be entered in its minutes and except for residents of cities and towns as provided in paragraph 5 of Section 1324.2 of this title any individual who fails to become a participating member within thirty (30) days thereafter shall not be eligible to hold office as a director, nor shall any individual, firm, partnership, association, or corporation which fails to become a participating member within ninety (90) days after such declaration be qualified to participate at any meeting or vote at any election held thereafter unless such individual, firm, partnership, association, or corporation shall thereafter become a participating member. Each landowner within the district shall subscribe to a number of such units in proportion to the extent he desires to participate in the benefits of the improvements. As long as the capacity of the district's facilities permits, participating members of the district may subscribe to additional units upon payment of a unit fee for each such unit. Owners or tenants of land located within the district who are not participating members may subscribe to such units as the Board in its discretion may grant, and upon payment of the unit fee for each such unit shall be entitled to the same rights as original participating members.
Okla. Stat. tit. 82, § 1324.12