Thinking of building a yourself an outdoor man room or office? Skip the normal, bland pre-fab game and check out the Kithaus K3 (starts at $29,500). This modern building uses a proprietary clamping system to make installation quick, easy, and virtually waste-free. All of the lightweight, anodized aluminum pieces are pre-cut and drilled in Southern California and shipped to you for on-site assembly, which takes only a few days. As a bonus, the Kithaus is built with eco-friendly materials, and you can order one complete with decks, canopies, and louvers for under $45,000; solar and furnished packages are also available. It's the ultimate adult treehouse.