Alleged killer Nathan James Carman has put his sprawling fixer-upper farmhouse in Vernon, Vt., on the market for more than double what he paid four years ago as he digs deep for cash to hire a lawyer.Built in 1850, the three-story, 6,207-square-foot property, which the 24-year-old Carman gutted down to framework and has been restoring while he lives there, is billed in real estate ads as “a rare and amazing opportunity” with “endless” possibilities.