The commission and units of local government administering ordinances with provisions similar to the real estate provisions of the law against discrimination are authorized and directed to enter into cooperative agreements or arrangements for receiving and processing complaints so that duplication of functions shall be minimized and multiple hearings avoided. No complainant may secure relief from more than one instrumentality of state, or local government, nor shall any relief be granted by any state or local instrumentality if relief has been granted or proceedings are continuing in any federal agency, court, or instrumentality, unless such proceedings have been deferred pending state action.