I myself was a pretty big Magic: The Gathering fanatic from 18 – 21 years of age. Though I didn’t setup any website about it, I did cojoin a site related to Dungeons and Dragons content and provided GM tools written in excel for download. At the time I never had much interest in branching out and starting my own sites for profit and 10 years later I started up my blogs. Had I only started ten years earlier I would be in a vastly different place than I am now, but as they say hindsight is 20/20
I stopped using this method once I started my own card game site (more on this below), however I still believe niche collectables, particularly in a market that you really love, is a fantastic starting point to gain experience making money online. Like eBay you can make money selling secondhand items in community sites if you can find a way to source product at cost or below. It’s not a model that has much margin so again the challenge is to scale if you want to make significant profit.
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.