JERSEY CITY-A portfolio of five mid-rise apartment buildings, all located here, have been sold for $10 million in an all-cash deal. The sale, announced by Harold Gerber and Frank Somma, whose firm, Gerber/Somma Associates of Hackensack brokered the transaction, amounts to an average of just under $67,000 per unit for the combined 150 units.The seller was a New York-based affiliate of J.S. Management LLC, represented in the transaction by Richard Kelin of the West Orange law firm of Feinstein, Raiss, Kelin and Booker. The buyer, who was not identified, was a group counseled by attorney Saul Kaszovitz.Four of the buildings sit on the fringes of the Journal Square business district and PATH Transportation Center, including 317-319, 321 and 343 Fairmount Ave. The final building in the group is the three-story asset at 62-64 Kensington Ave. The five buildings are currently fully occupied, according to Gerber.