Unaffordable Payments (7e) Trading a Payment Subsidy For a Share of Appreciation Who This Calculator is For: Lenders who have ARM borrowers who are facing rate resets they can't afford, who may want to offer a payment subsidy in exchange for a share of the future appreciation in the borrower's house. What This Calculator Does: This calculator compares the present value of a share of appreciation in the borrower's house with that of the subsidy paid [to] the borrower, over the same time horizon.