Here are the criteria for my concept. It's basically a classifieds site, but I have some bells and whistles that will really take it to the next level. So can this be done with WordPress?

How this site needs to work:

#If not signed in, home page shows sign up button (Facebook only) and description of what's inside.
#Upon account creation, user sets standard search criteria to show up in general feed. (Town(s), categories.)
#When signed in, home page shows general feed based on set criteria.
#Users can post from a button on every page. Post needs photo, description, location, price, contact info.
#Users can favorite posts so that they can easily find them later from a "favorites" page.
#If logged in, above the feed is a search area. (Town(s), categories.)
#Allow commenting on posts.
#Allow tagging of other members on posts.
#Allow private messaging between members.
#Posts will show available, pending, or sold statuses.
#Posts auto-delete one hour after being marked sold.
#Posts include share button to share on Facebook.
#Two ad spaces above search/below navigation bar.
#Allow featured posts to be pinned to top of feed, only by Admin.
#Pinterest type auto-reveal more posts while scrolling.
#Two ad spaces every 5 rows of posts.
#Allow user types. (Standard, Moderator, Admin.)