PHILADELPHIA — On behalf of a family office investor, JOSS Realty Partners has purchased a mixed-use building in the Fishtown neighborhood of Philadelphia for $6.3 million. Rittenhouse Realty Advisors brokered the sale and Leopard Point LLC was the seller. The 14,500-square-foot property, located on 18-20 W. Girard Ave., includes 15 new apartment units above a street-level commercial space occupied by Sherwin Williams. The fully leased building offers one- and two- bedroom apartments as well as a rooftop deck. In recent years, Fishtown has seen an influx of upscale art, entertainment and dining establishments, as well as a rise in housing prices.