Hi! I did some research about free 3D software for Mac and have seen some tutorials about SketchUp. It's an easy to use app, I did like it. But it does not solve my problem. I wish to make a plan of a house, and than make a 3D projection. In SketchUp, the guy show how to make a "illustration" of a house, since the walls got no thickness. It seams the purpose of the app is to make a house to put in some game or just illustrate a landscape, etc..
I saw a lot of apps to sell, they are expansive for somebody to start learning, make some amateur jobs (maybe to draw my own house), there is not even a demo to see how it works. I know well A.I. and Corel Draw, but these software does not have the concept of a wall, just inside and outside lines, it's what a got and know how to use.