The trustees shall establish and collect charges for services and rentals for use of facilities furnished, acquired, constructed or purchased from the proceeds of the securities sufficient to pay the principal or the interest, or both, on the securities as they become due and payable, together with the additional sums as may be deemed necessary for accumulating reserves and providing for obsolescence and depreciation and to pay the expenses of operating and maintaining the facilities. The trustees shall establish all other charges, fees and rates to be derived from the operation of the hospital or any other facility of the rural health care district.