This is our treehouse. We built it over a year or so, starting in June of 2003, and spent ~$5,000 dollars. It is warm and cozy and the winter. In the summer, all of the windows make it feel like you are sleeping outside. It is ~160 sq.feet. with insulated walls and double pane windows. Most of the materials were salvaged or bought from the Recycle North Building Materials Center (they take down buildings and resell the parts- they rock!).