It's all down to strategy. For someone whose skills lie in design and execution rather than consistent on going marketing, creating and selling websites can be a great way to quickly make money. Starter sites (no revenue & little to no traffic) go for between $75 and $300 USD. Alternatively, a site may be making money but not enough for someone to warrant spending the extra time and effort on promotion. In this case, it's ideal for someone who has the time to promote it, but maybe doesn't want a starter site or cant create one from scratch. There's also hosting on the back end which, with say 15 sales in a year can bring in an extra $1800 revenue, literally from doing nothing. If you scan some of the site for sale listings on our site, you'll be surprised at the variety of sites which sell.
I think advertise on your site or blog is also good methods to make money. Currently I am earning money through google adsense. I don't know more about affiliate marketing. But as popularity, affiliate marketing is also the popular ways to make money.
If you have a blog you can monetize it by putting ads like adsense. You also do some paid post. Some people do Pay Per Clicks too. You can aso use your blog to gain some Twitter followers and then you do some paid tweets.
I feel Google adsense is simplest and quickest, but due to high competition you have work hard initially. But it good for bread and butter
I would refer you here http://www.theinternetmarketingsuperclass.com/makemoneyonline for the information you are looking for. They outline professionally easy ways of making money online, and these are not scams.