The best thing about eBay – the abundant traffic – is also the worst thing. Barriers to entry are low on eBay, meaning competition is fierce. When competition is fierce, profit margin is slim. Unless you can find some form of competitive advantage through your supply chain, how you create listings, or you have a means to increase volume, you’re not going retire rich thanks to eBay.
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.