The numbers behind this elaborate mansion on the shore of Lake Champlain tell the story: 60 rooms, 10 chimneys, 1,400 acres. It's a whimsical house, a tourist attraction in and of itself (in fact, there's an admission charge to the extensive farms on the property). Yet from May through October, you can sleep here and pretend it's all yours. Built in 1899, the sprawling Edwardian "farmhouse" is...