I believe there is nothing like Google Adsense where let the users earn money from Advertising at Facebook. Facebook is a place to network and interact with customers and prospects. The owners must have products or services that offer the customers.
Facebook is a social networking site and there are chain of peoples from one friend list to another, so you can get lot of traffic for you website by promoting your website on facebook.
You can earn money off Facebook through Apps and Viral scripts. Look into them it should give you some ideas on how to make money off facebook. I know it was quite big last year i dont know what the current market is doing in making money off facebook now.
These days its quite difficult to get traffic from Facebook and you need a lot of experience for getting traffic from Facebook.
I think the most important factor that you should consider in facebook is Traffic! if you post something valuable, updated and attractive people will like you and you get many visits to your site or blog.
I f you have website then make its page on facebook it is very easy, when people join or like ur webs page on facebook they start coming to your site then you can monetize your facebook presense