A four-part series on how banks deny minorities home loans three times more than whites. Part One discusses how Blacks and Hispanics face significantly higher rejection rates than do whites. Part Two discusses how buyers in minority neighborhoods have an especially hard time getting a mortgage, regardless of race. Part Three discusses how few lenders on Long Island have managed to make minority loans a sizable part of their business. Part Four discusses how sanctions for not living up to federal fair-lending requirements are rarely invoked.