Is it possible to require users to log in/register before seeing contact information for the adds?
You couldn't hide just the address or contact on an advert without some customization of the theme. You could require sign in to view the site, but that would hide the entire site from users that are not signed in. Might be a good idea for a plugin.
Is it possible to charge a registration fee via paypal?
This would also require customization. It is possible that there is a plugin for this somewhere but we couldn't guarantee that it would work with our theme. You migh want to look into a membership plugin, specifically.
