Listing an item for sale is as simple as checking the sell box when creating a post and setting a price. Users can list the post for sale later too.
Listings are built directly into posts under an expandable tab. Posts show the last sale, top offer, highest bid, and the sale time left. For owners, it holds the option to list for it sale and to accept bids. For everyone else, it holds the option to make an offer or buy now.
The standard royalty for NFP sales is 5%. This means that when a post is sold by someone other than the poster, the poster gets 5% off the sale.