I've been a professional architectural visualization freelancer for the past decade.
But over the years I've developed a side interest. I sell commercial 3d models on Turbosquid... and things have gone pretty well.
So I'm now beginning to write some guides and tutorials to help other 3D artists to do the same thing.
I really think its worth it for people in our profession.
Whenever you have down time between clients you can spend your time creating something of value for others, and make some extra income !
You'll find my first post on this subject on my blog here:
8-ways-find-3d-model-ideas-sell
Feel free to leave me a comment :-)