How do websites like goiit.com, faadooengineers.com, and pagalguy.com get started? What is the story behind these websites?

I've worked closely with the founder of http://managementparadise.com over the past few years. The earnings are very high and as far as the grapevine goes, its in crores. http://ManagementParadise.com  today is a network of sites and a few popular ones they own are : http://BMS.co.in http://B-school.com http://MBAs.in http://BMM.co.in http://CPT.co.in http://HSC.co.in http://BBA.co.in and probably several more. The last one that resulted into losses and shut shop was http://OnlineMBA.co.in where they were selling affordable online video lectures made from faculty of premier institutes. Anyway, how it started is where the founder : Mr. Kartik was studying himself in college at 19 yrs of age and wanted to bring together students from various colleges to facilitate peer to peer learning or as we now call it "social learning". The concept became a hit but did not make money for several years. Just when Mr. Kartik was about to complete his MBA the concept picked up in monetary terms as well - probably by chance. The money made was poured back into the business and we still operate from a very small garage like office. Most employees are virtual and most profits are pumped back to start new experimental ventures or sustaining existing ones. Does that answer your question?

The best place to know about a website is "About Us" page, unless it's a messed up and don't tell the things you would like to know. How they started, I don't know. But sometimes the owners share their stories on website or other places. Find them yourself, or wait for the representatives if they volunteer to tell here. How much revenue they can earn through this? Nobody will tell you this unless the company is https://buffer.com What are possible areas from where they make money? If you have gone through fadooengineers.com, what you see? There are ads everywhere, top, bottom, left, right. That's where the revenue come from. pagalguy.com is a a online community, they have articles, forum and information about examinations. You don't see ads on their website, but they are offering some kind of advertisement, if you go through their about us page. This can be allowing other education portals to advertise via sponsored content or banners. Unfortunately goiit.com not opening, so I can't comment anything on them. If you are unable to find what's the revenue source of a website (by visiting website), they may be trying to expand their user base, subscribers, etc. Later when they have numbers, a revenue model can be implemented.