What is the ruling on a person agreeing with a lender to purchase an apartment in the borrower's name, whereby the borrower pays an annual rent to the lender commensurate with his share in the value of the apartment, in addition to repaying the principal loan in installments?

This is blatant usury (riba) because the lender did not obtain the annual rent except in exchange for the loan. A benevolent loan (qard hasan) makes the apartment the property of the borrower, and the lender has no right in it for which he would deserve rent. Every loan that draws a benefit for the lender is usury.