And that’s not the end of the aid Google could be legally entitled to. Oxford Properties made another clever move when it bought the property back in January: It purchased only the portion of St. John’s Terminal south of Houston St., leaving the northern segment, and scaled-down plans for housing there, with its original developer. As it happens, businesses that significantly improve properties south of Houston St., already have Manhattan employees and expand their downtown workforce by at least 25% are entitled to claim a tax credit worth $3,000 a year, for a dozen years, for any employee who moves in at the outset — but only for those workers relocated from outside New York City.