Can my users sell products

That’s exactly what the Frontend Submission extension is for: https://easydigitaldownloads.com/extension/frontend-submissions/

Thank you ??

So the main plugin is free, right? But the frontend submission I need to pay for. I dont need to pay for the main plugin?

That is correct.

The main plugin is free and is fully featured. The extensions provide additional features.

Looking at your plugin for a client. For the Front End Submissions add-on, is there a way to auto approve submissions, once the user is registered?
Thanks!

Yes, there is an option for auto-approving submissions.