I'm not a Facebooker, do they charge fees? In lurking on there I see sellers get their phone numbers blanked out if they try to bypass FB messaging.
No, they don't charge. In general, it's a fairly easy way to move items locally. Depends on the thing you're selling. I would not recommend for a nation wide type thing. Also depending on what you're selling, you'll get all kinds of lookie-loos and clueless people. Read the seller notes, you'll see the experienced ones obscure their contact info to hedge against spammers scraping data from the site. And stuff like "if it's still up, it's still available" "will not respond to is it still available messages" and such. People can send a generic query about an item, personally those drives me nuts. Just says the looker doesn't care enough to flesh out a decent query on the item. Took about 20 months to sell the 70 Mustang roller chassis. Lots of bullshit, will you take X, I'll come look at it (never shows), when I sell X/Y/Z I'll buy it and the best "will you take payments". No hell no.
We use it mostly to move household items and most of that is come and get, if you're a reseller get lost. We've given 2 or 3 TVs to single moms, etc. But you have to weed out the junk store people from other cities.