If you've never created 3D characters before and want to explore whether it is feasible to start learning character creation with purpose of selling them on stock market, then my advice is - forget it - in order to be able to create high quality appealing 3D characters, you would need to have years of hard learning and practice and the final profit from this activity might never pay off. On the other hand, if you're already experienced character creator who works in the industry and just looking for opportunity to sell your models from previous projects, then just go ahead and upload few of them. It will cost you next to nothing, but will be great opportunity to see whether your models are in demand for customers. You will get much more useful information from this, than from reply from random dude on the internet.