I have been testing the add listings features. I created a free listing as a subscriber (not admin) and I noticed that once this is created there is no way for me (as the subscriber) to upgrade the listing. I am guessing they would be able to create a new paid for listing but that would create 2 listings in the directory based on how I described this transaction. Once the free listing is created the user can't modify any of their content either. Is this also the case with a paid listing? It would be nice to be able to allow the user to able to not only create a new listing but also to edit and upgrade it.
We have updated the theme with added the feature that you wanted. Hence user can add free listing and if they interested to upgrade listing, they can do this by selecting upgrade option. This feature is available in listing edit option in user's dashboard.