Coruscation

Pressing further, the developer sent a letter to all the renters in January offering a deal -- and doing the math to help them see its appeal. Renters were paying $6,500 a month for a two-bedroom two-bath apartment with 1,400 square feet of space. Mr. Gladstone offered the unit at a 10 percent discount from the original asking price, which dropped the price tag to $1.75 million. With 70 percent financing at current rates, the monthly mortgage payments should be about $6,300 a month. The common charge for the building is about $1,200 a month.

But the tax savings -- including the mortgage interest deduction on the federal income tax and local homeowner tax relief programs -- would effectively bring an owner's net monthly payment to about $5,100, according to the letter. That would mean monthly savings of more than $1,000.