(1) for housing accommodations, rents in force and effect on July 1, 1947;
(2) real property used for business purposes or on which superficiary houses are constructed, rents in force and effect on July 1, 1947;
(3) for newly constructed housing or business accommodations first rented on and after the aforesaid maximum rent date, or accommodations changed on or after such date, so as to result in an increase or decrease of the number of dwelling or business units in such accommodations, the first rent for such accommodations after the change or maximum rent date as the case may be, but in no event more than the maximum rent provided for such accommodations by an order of the Rent Control Officer upon application properly made; and
(4) for housing accommodations or real property used for business purposes or on which superficiary houses are constructed, not rented on July 1, 1947, and not covered by clause (3) this section, the last rent in force and effect prior to July 1, 1947.