How To Buy A Masterpiece From Prairie School to International Style, important 20th-century homes are being snapped up by collectors. By Mark Van de Walle "I really didn't need another one," says David Zander, recalling his recent decision to buy the Schaffer Residence, a redwood-and-glass house in Glendale, California. Designed in 1949 by Frank Lloyd Wright protégé John Lautner. "I mean, it's not...