But it won't be a hotel. It will be a timeshare, developed through the company's Hilton Grand Vacations Co. division. The 28-story property on West 57th St. between 6th and 7th Avenues marks the first time a building designed exclusively for timeshare accommodations has ever gone up in Manhattan. Timeshares are still not a huge source of revenue for Beverly Hills-based Hilton, but growth has been considerable, with 2005 revenues of $554 million, up 32 percent from a year earlier. Profits in the first half of 2006 were up 20 percent. Several of the major chains have taken a liking to time shares, mostly through properties near existing resorts. Hilton's effort in New York would seem to take the concept a step beyond.