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 section 76-817 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:

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

(2) Payments due under duly recorded mortgage and lien instruments.