i think the answer depends on your intent. if you're just trying to come up with a layout for your house, then Google Sketchup is free and a very good tool. if you want to create blueprints which could be used to build a house, then you probably want to hire a professional since a blueprint which has all the necessary information for permits and sign off, and is in a format which a professional builder could use, is a much bigger issue and not something you can just do.
