Almost all dating sites that have gained traction launched with dummy users. Once they start getting real users, they scale back on the fake users.
Both OkCupid and Plentyoffish likely also used bots that message new users from those fake accounts in order to keep the interest of the initial users.
Is that a dirty tactic? Yes. But it's very hard to create any social network without this strategy. Reddit did the same. Alex Ohanian created 10,000 fake users and posted content until they didn't need to do that anymore. Look at Reddit now!
With classified ad sites, I would think they're leveraging the elephant in the room -- Craigslist.
i.e. They probably write a bot that scrapes Craigslist every hour and post the ads on your own platform. And scale back when real users start posting enough content.
When Bright Journey launched, we were able to leverage a previously closed community (OnStartups) to get the initial users. A hefty chunk of those users were able to come to Bright Journey as the other site had closed. Without users from that community, we would have had a really tough time getting any momentum on this site.
So it essentially comes down to using one or more of these:
Many scrape content from other classifieds sites. This builds the listings (granted, from another source) to look more like a non-one-person site.
Thanks Nishank for the valuable response! and based on your response i have confirmed what other classified ads are doing or dating sites =)
I've done the post content myself however, it is not sustainable since i'm doing it manually it seems like i need to get a content curation service to curate a content that will be posted in the website...