A members site?? Help !

I’m Rebuilding my wordpress site. and i want to make a members site where people can post there own stuff including pictures..and maybe set up there account on my site through paypal. Can anybody point me in the correct position, like plugins for safety precautions. membership..etc…..any advice would help. im not looking to purchase your stuff either. let me know thanks!

P.s. i want people to have capabilities to buy from independent people….that kind of stuff…where they can log in post etc…almost like a classified

Any suggestions will help even if i didnt ask a question about your advice, Thanks