Making money with mini sites is a way of earning your income online, but I'll say it from the beginning, it shouldn't be your only source of income. They rely solely on search engine traffic most of the time, and the algorithms can change at any time. I wouldn't quit my day job yet if my income would be made only from search engine traffic. Still, they can be nice additions if you choose your niche right.
Mini sites usually have just a few articles, centered on one or more keywords that have low competition and they're easy to rank for most of the time. They're the fire and forget type, meaning that you set them up, write the articles, do a bit of promotion and then forget about them. If you choose your keywords right, they can make anywhere from a few cents a day to $10 or more. It all depends on how much work you put in finding the right keywords for them.
Money-online if you find some good related keywords with very low competition and you're interested in the subject, I'd suggest building a blog on top of them and convert those search engine visitors into subscribers. If you have no interest in the subject, muster enough strength to write a few articles and make a mini site out of it. Building a blog requires much more time, but in the long run you get those repeat visitors, and you also have access to Text Link Ads and paid reviews if you promote it. With mini sites you usually have just Adsense and affiliate programs. Another option would be building a community if the term is searched enough. A bit more works again if you want a forum, but it's an option.
A bit more before we start. I decided to write here the real keywords that I'm going to use for this tutorial, because this is more of a guide, and less of a case study. The fact that I'm saying which they are from the beginning and the address of the mini-site, will mess with the results of the experiment, but at least you get to see everything so you can apply them and make your own mini sites. With mini sites you usually have just Adsense and affiliate programs. Another option would be building a community if the term is searched enough.
Keyword Research
This is the most annoying part for me and a major time drain. It may take a while to find a few keywords that have a sufficient volume of traffic and they're also easy to rank for. Don't overdo the study of the competition though. You're not putting 2 years of work into this, just couple of hours, so the risk is ok.