No such corporation shall disburse as administrative expenses during any one year, except upon approval of the Director, a sum greater than 20% of payments received from subscribers during that year. The term “administrative expenses” shall include all expenditures for non-health services and, in general, all expenses not directly connected with the payment for health services, but shall not include expenditures for purchasing, acquiring, leasing or renting land, premises, facilities, equipment, instruments or supplies needed or useful for the purpose of rendering health services, and shall also not include expenses of soliciting subscriptions.