You can still use sketchup 8 and prior for commercial use. You can download previous versions of trimble and google sketchup here.
John Bacus, SketchUp Product Manager:
“The new ‘non-commercial’ terms in Sketchup Make are intended to prevent use of that product for commercial work of any kind. Users of Sketchup v.8 are not subject to that term, so obviously you’d be free to continue to use that product for any use, commercial or otherwise.”
This topic has been discussed at length on the forum already here.
The only other quality free program I’m aware of is blender, but I don’t know about their TOS.
Also… you may want to look at this post that helps visualize how affordable sketchup is compared to other software…