Two ways.
First, the site is USER MODERATED. Users flag bad ads. Users report severe spammers. Users report bugs. Users offer advice to other users when there are site-use problems or when users can't figure out why their ad was flagged. The entire site has about 30 paid employees. They run the code and the servers. The rest of the site is run by the users. As long as everyone does their fair share of work flagging the occasional bad ad, it works.
Those thirty employees, the servers, and the internet bandwidth are paid for by the Job, Therapeutic Services, and Real Estate ads in a few cities. Only a few major cities charge for ads, and the price varies by the category. Think $25 or so for most of them!
So...with the users "paying" for the site with their own efforts, it doesn't take a lot of money to keep the site running and working well. The necessary money comes from a few ads types in a few cities, such as Real Estate in New York.
Craigslist makes it money by charging six of it's largest cities $25 for job listings, San Francisco job listings $75 and New York $10 for brokered apartment listings. So when you add it all up that a lot of money for site that offers free listings in well over 100 markets. It's like buying a stock and selling it back.....kinda like nikey east bay etc....
They charge for some of their listings in some cities (mostly real estate and help wanted).
I agree with above answer it saves time for small business.
I don't see ad on craigslist, how the website sustain itself?
