questions about classifieds

Wanting to setup site to be able to view parts of the classifeds but not able to view entire post without becoming a member.  What I am trying to accoplish is a non-profit site, so I need people to view the person or persons needing help.  Then if they are interested they can sign up to donate to that cause?  Also, is there a way to put a paypal form button into the classified without it being stripped from the code?