How to disable free ads posting? Or how to force users to pay for ads posting?

The best way to disable posting of free ads (or to force users to pay for ads posting) is to:

1. Disable or delete all the free packages in the "Admin panel → Settings → Packages"

2. Enable the "Allow listings to be reviewed by Admins" option from the "Admin panel → Settings → General → Listing Form"

3. Reduce the "Unactivated Ads Expiration" field's value in the "Admin panel → Settings → General → Cron"

4. And make sure that the "Ads Cleaner" command is properly configured in the cron job tab on your server. 

Please see this article for more information about that:
http://support.laraclassifier.com/hc/articles/19/configuring-the-cron-job.

NOTE: All the paid ads will automatically be approved (without admin approval).