Read this https://help.grabcad.com/article/149-community-values-and-guidelines clearly, you'll find this:
Do not try to make GrabCAD members pay for your model. While some of our members create their designs and models for the love of the craft, and are happy to share their work for free, others look to CAD development as their livelihood and career, and are looking to be financially compensated for their work. GrabCAD is a free model-sharing community, and our content should be available to anyone who signs up. Anyone who wants to charge for their models should instead check out CGTrader, where they are allowed to do so. But charging for GrabCAD models is not allowed.