in my impression vendors do sell stuff that they had been done for their own anyway. Thats how i do it ... I build my stuff for my comic i am working on and because i have it, i sell it too. But beeing a 3D Modeller only for money making purposes, ... well, tough job i guess.
You wont be making 4000$ a month. THat would need lot of luck, expirience and a good sense and understanding of what people need......

and: I still think vendors and merchants here do what they do cause they feel its an obsession, a hobby. Very little may make 3D Stuff only because of the money. There are much easier way of making money with litlle stress and work....

my 2 cent on this ...

3-D-Cs Facebook Page: 3-D-C on Facebook

Check the K-Azonica Story and World Evolving:   K-Azonica

Check my website and products and the large freebie section:   3-D-C