Long gone are the days of eBay fees and consignment stores -- now you can sell your stuff, and buy other people's stuff, on Facebook without having to fork over any commissions. Between Facebook's own Marketplace and the hundreds of "Buy, Sell, Swap" groups popping up on the platform, it's never been easier to have a garage sale. You don't even need a garage, just a Facebook account, a camera, and wares to shill. It should be noted that none of this is a commercial enterprise -- it's the private sale of individually pre-owned goods in peer-to-peer marketplaces.
Facebook has a location based marketplace
When you login to Facebook from your iPhone (5 and up) or Android (only mobile devices) with your location services switched on, you'll get an icon in your menu that directs you to Facebook's Marketplace. The Marketplace is to "buy and sell locally" and you can set the radius you'd like to peruse from your immediate location up to 100kms away. You must be over 18 to use Facebook's Marketplace, and so far it's only available in the US, UK, Australia, New Zealand and Mexico (although there's plans to expand). The Marketplace is designed to be "a convenient destination on Facebook to discover, buy and sell items with people in your community."
There are also local, special interest buy, sell, & swap groups
Private users have also set up a variety of different Buy, Sell, & Swap groups -- you can search for them with Facebook's search function. Some are general used clothes or goods groups, but others are more specific -- for instance, I'm part of two separate groups for the selling and swapping of Zara clothes only.
Request an invitation
Most of these groups are private, so you'll need to request an invitation to join. I've never had a problem being accepted -- admins are generally happy to grow their community. Sometimes you'll need to have your location services switched on to be accepted, if the community has specific neighborhood or geographic restrictions. This is because as well as sellers offering postage for small items like clothes, there can also pick-up necessary when people are selling bigger items like furniture.
Join discussion groups too
That's right, groups also have ancillary discussion groups. Here you can ask for advice (for instance, if you're in a high end designer buying group, you might have questions about caring for and repairing luxury items, or for how much you can expect to sell second hand goods) and get to know the people in the community you're selling to and buying from.
Use Facebook's cross-posting feature when you're selling
The best part of all of this is when you post a sale in Facebook's Marketplace or any of the groups you frequent, Facebook gives you the option to cross-post in Marketplace and the other groups -- you literally just have to tick boxes once you've finished filling out the description and uploading photos of the item you're selling. It's stupidly easy, and totally free.