There’s a reason that outfits like Corcoran, Thor Equities, and Prudential Douglas Elliman open their wallets for the proposed Brooklyn Waterfront Greenway. For them, 14 miles of car-free bike path along the East River could deliver a crush of renters and condo-buyers to neighborhoods otherwise hard to reach. The rest of us proles will still be able to enjoy the trip from Sunset Park to Red Hook, through Vinegar Hill and Greenpoint, on to Williamsburg and points beyond. Goodbye, G train, and hello, Schwinn. Conceived by Milton Purlyear in 1993, the Brooklyn Waterfront Greenway began a steady advance this year from abstraction to reality. The city Department of Transportation began putting up signs for the route in Red Hook. An overhaul of Kent Avenue, at the western edge of Williamsburg, included designated lanes for bikes. It’s possible that permanent pathways could replace these interim fixes for a total of five protected miles before Mayor Mike leaves office in 2009. Welcome to the new New York.