If Maria finances the purchase with a $180,000 mortgage at 4%, her excess income is reduced from $2,000 to $669 because of the mortgage payment, but her financial assets are reduced only by $20,000 to $280,000. The future values are $164, 526, $509,684 and $313,486, which sum to $987, 697. The future net worth is the same in both cases because I assumed that Maria’s financial assets earned the same return as the rate she paid on the mortgage.