Hi Julie. Thanks for your interest in our plugin suite.
All our paid plugins are either an add-on for the free The Events Calendar plugin or the free Event Tickets plugin.
Our Community Events (CE) add-on allows your site users (and optionally anonymous / non-logged-in visitors) to post events to The Events Calendar.
If you also have our PRO add-on, the front-end CE form can support PRO’s Additional Fields functionality.
If you also have Event Tickets Plus and Community Tickets, users can even sell their own tickets (you can take a cut of their sales).
Last but not least, we have a pretty great Refund Policy so you can buy one or many of our add-ons and thoroughly test them.
So please look through these choices and let me know if you have any follow-up questions for your specific use case.