(a) All sums assessed by the administrator, or the board of administration, or other form of administration specified in the bylaws, but unpaid, for the share of common expenses chargeable to any apartment shall constitute a lien on such apartment prior to all other liens except only (i) tax liens on the apartment in favor of any assessing unit, and (ii) mortgage and other liens, duly recorded, encumbering the apartment. Such lien may be foreclosed by suit by the administrator, or the board of administration, or other form of administration specified in the bylaws, acting on behalf of the council of co-owners, in like manner as a mortgage of real property. In any such foreclosure the apartment owner shall be required to pay a reasonable rental for the apartment after the commencement of the foreclosure action and the plaintiff in such foreclosure shall be entitled to the appointment of a receiver to collect such rents. The administrator, or the board of administration, or other form of administration specified in the bylaws, acting on behalf of the council of co-owners, shall have the power to bid in the apartment at foreclosure sale and to acquire and hold, lease, mortgage and convey the same. Suit to recover a money judgment for unpaid common expenses may be maintainable without instituting foreclosure proceedings.

(b) Where the mortgagee of any mortgage of record or other purchaser of an apartment obtains title at the foreclosure sale of such a mortgage, such acquirer of title, his successors and assigns, shall not be liable for the share of the common expenses or assessments by the co-owners chargeable to such apartment accruing after the date of recording such mortgage but prior to the acquisition of title to such apartment by such acquirer. Such unpaid share of common expenses or assessments shall be deemed to be common expenses collectible from all of the apartment owners, including such acquirer, his successors and assigns.