Hi guys, thank you for the great job you are doing. Anyway, I would like to suggest that you add an option in the plugin that allows:
1) That visitors can publish ads for free up to a certain monthly or weekly amount (like 10 per month, for example).
2)Allow that when the monthly limit is reached and the user wants to publish again, there is a message notifying them that they have reached their limit and must pay the publication fee.
Many classifieds sites do this and it works very well as a business model for a classifieds website.
Thank you and I hope I have presented my suggestion clearly.