Upon the sale or conveyance of an apartment, all unpaid assessments against a co-owner for his pro rata share in the expenses to which § 27-31-190 refers shall first be paid out of the sales price or by the acquirer in preference over any other assessments or charges of whatever nature except the following:

(a) Assessments, liens and charges for taxes past due and unpaid on the apartment; and

(b) Payments due under mortgage instruments or encumbrances duly recorded.