I'm planning to have a house built. I want to draw up some sketches on the computer, so I am looking for a program that can help me do this. It doesn't have to be a professional architecture tool; in fact that would be too complicated just yet (but maybe later on, for the detailed work...?). A simpler tool would be better.

Features should include such things as ability to draw and move walls (not just using simple boxes), calculate room/floor area, add windows and doors, and the like. That's why Inkscape or OOo Presentation won't do. On Windows, a friend would just download a cracked professional architecture tool but that is not what I want to do.

Suggestions?