A regional education service center that acts as a fiscal agent or broker in connection with an agreement between two school districts under Subchapter E, Chapter 49, may not, unless authorized in writing by the district receiving transferred funds in accordance with the agreement:
(1) be compensated by the districts in an amount that exceeds the administrative cost of providing the service; or
(2) otherwise retain for use by the center any amount other than the compensation permitted under Subdivision (1) from the funds transferred between the districts in accordance with the agreement.