You don't have to be a math major to understand that free ads can be a profitable way to grow one's business. I have written in the past about Craigslist, but will today focus on a similar site called BackPage.
It's fair to say that Backpage may not be as widely known as Craigslist, but it may well begin to catch up, in part because of Craigslist's own success.
If your business has posted on Craigslist, you may have experienced a common problem. You will get calls the day you post and maybe the next day. But within a couple of days, if not a couple of hours you end up getting pushed so far down on any given list category you may as well be invisible.