Make money online can be time consuming and very confusing. One way of making money online is by setting up a blog.
There are many ways to monetize blogs and you can literally create micro-niche blogs on every subject imaginable - drive traffic, and monetize via adsense or a vast array of affiliate offers.
The most successful method is measuring and creating a highly focused blog on a particular niche you are interested in, finding affiliate marketing products through cj (commission junction), cb (clickbank) or anyone of hundreds of other affiliate program networks. I use Compete, mostly. Many of the CPA and higher profile networks do expect you to be of age, but you can talk to them when you apply.
Once you identify your maket and what you can actually sell to your market, you can optimize your individual pages to promote certain products or CPA offers, as well as monetize through adsense - you want to TARGET your pages to your audience so relavent ads show up and you are of course showing relevant products. Gone are the days of putting up mass generated junk pages with general adsense ads that aren’t targetted at all to your visitors. If you have low clickthrough rate on your ads on your pages, Google pays you less and less and less. The higher the clickthrough rate, Google believes your pages are more relevant because obviously people are clicking on the ads (because they are relevant). The name of the game is to show people USEFUL information. The web is doing a good (better) job of weeding out all the garbage and riff-raff, which gets rid of all the bad-apples and allows internet marketers like us gain some credibility back.
In summary, this is only one of the free ways to make money online but it is very simple. If you can set up a free blog, free Adsense account and add content to your blog about a given subject then you have a free business that you can either build or duplicate time and time again. You will be pleasantly surprised to know there are many more ways to monetize your blog, free ways to generate traffic to your blog and even free ways to get your site on the front page of some of the Google search results pages.