Determination of charges relating to income-producing

projects. Such county, independent rural, union high and municipal board of education or board of regents shall be required to make such charges for the use of said building, improvement or facility purchased or erected hereunder and the furnishing of the services for which same is purchased or erected and used as will return annually a sufficient amount to pay the annual requirement for repayment of principal and interest on such bonds or other evidence of indebtedness; and in addition thereto may make additional charges for the use of said building, improvement or facility and services to return a sufficient amount to pay all necessary costs and expenses of maintenance, upkeep and any required repairs thereto and all necessary costs and expenses of furnishing all services in connection therewith, and sufficient to create a reserve fund not exceeding $10,000.00 to be used for repayment of said indebtedness; but said county, independent rural, union high and municipal board of education or board of regents shall make no further or additional charges for the use of said building, improvement or facility and the furnishing of the services for which the same is erected or purchased and used, to the members of the student body, faculty, instructors and other employees of such institution.