Any great to place for a beginner to sell 3d models online?
TurboSquid is one of the larger sites and their database is very extensive. I haven't personally used the site but I visit it frequently when in search of models (If GrabCAD does not already contain a likewise part)
You can upload and set the price for all of your work, whether or not it brings in sales is up to you :)
Like ML said. Turbosquid is a very good place.
You can check here too:
They have more formats and better organized than Turbosquid.
If you are selling models for 3D Printing, Shapeways is a great place to have a own shop.