Is there a program that I could download on my computer for home design for free?

i would just like to design my dream home just for fun and I just wanted to know if there's a place online in which I could do that for free?

Details:

1. yes. google sketchup is autocad (architectural program) that is completely free. search for it on download.com
2. if you have linux theirs gcad and freecad both are low quality but their free their no autocad or primecad.I have a degree in autocad and drafting home design is going to take a while to do if you do it correctly