It's sometimes said that Manhattan luxury condominiums sell themselves, and a trip through our Manhattan condo listings will surely bear that out for a few NYC apartment buildings. But it's just an expression, finally, and most NYC luxury condos -- even the best of the best -- don't necessarily sell themselves. Yes, the Manhattan apartment market is surging, but with real estate watchers concerned about a double dip in the housing market and the local and national economies still sputtering, the investment of money and confidence required in buying a Manhattan condominium is no small thing. In reality, most NYC condos require no small amount of selling, which is where price cuts come from, among other things. Recently, developers have hit upon a new -- and, for once, very factual and very useful -- new marketing tool. That would be the approval of the Federal Housing Administration.