Cornerstone Property Group completed the sale of 339 East 90th St. The 5-story walk-up apartment building sold for $4.45 million. Abe Bichoupan of Cornerstone represented the buyer, NJB Realty, LLC while Lipa Lieberman of Cornerstone represented the seller, Schildbar Properties, Inc. The transaction occurred at a gross rent multiple of 12 and at a cap rate of 5.4%.