If you work hard enough to make a living as a vendor you're still not going to have time to invest into making a movie.
Between modeling, texturing, UV mapping, rigging and posersizing, and making catchy promo images and self promotions and everything it takes, you're pretty much working 12 hours a day.

If you don't put that much effort into it, then you;re looking at the lower end of earnings - which is $0-$500 a month. 

Also as was pointed out, skill and talent and having a feel for what people are interested and will buy in has a lot to do with how you'll do.

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Renderosity Store  Personal nick: Conniekat8
Hi, my name is "No, Bad Kitteh, NOO", what's yours?