They are everywhere, more people are building them every day. Are they making money? I would have to say yes from my limited experience. I am sure some make more than others, but I don't think it is that hard to make money from Adsense sites. The more sites you build the more money you can make.
In my opinion building Adsense sites are the easiest way to make money on the Internet that I know of. It may not be the quickest way, but it is certainly one of the easiest. I started building Adsense sites in late 2005 and within 2 months I was making a small amount of money with very little work involved, after the sites were built.
I built all my sites by hand with just one top level domain just to see what would happen. To my surprise it worked, I was bringing in 2 or 3 dollars a day. That doesn't sound like much, but I knew all I had to do was to build more sites with top level domains and I would be making a living off the Internet.
It all came crashing down for me when I lost my Adsense account. I was just getting ready to start building sites on a massive scale. Google would never tell me exactly why my account was suspended, but my guess is one person was clicking on my ads a little to often. Even though most of my traffic came from search engines, I did have a few sites on forums and once in a while I did run a few ads in traffic exchanges
I would not recommend having Adsense sites advertised where just one person could click on ads over and over again now, but at the time I didn't realize my account would be suspended because another person clicked my ads too many times, I understood asking another person to click my ads would result in my account being suspended.
I am not writing this article to teach you how to build Adsense sites, that would be more information than I could put in this article, but you can download my free ebook that will give you all the information you need to build quality Adsense sites. I would compare this ebook to taking a course in Adsense. You can get it free at http://ncave.com/sites/moneyreport.html
There are a few things I would like to tell you about Adsense that might help you though. It will take time to build the number of sites you will need if you plan on making a living from Adsense sites. You should plan on getting your traffic from search engines, the free ebook can show you how to do that. Before Adwords made a change in the keyword price many people were using Adwords for traffic, but it is not as easy to use Adwords for Adsense sites now.
There are some good site builders that can help you build sites much faster than you can build them by hand and my plan was to use one before my site was suspended. If you would just like to see if Adsense is something you would enjoy, you could start like I did just building a site by hand and if it pays off then you could find a site builder you like. You can also buy ready made Adsense sites, I would have also looked into this if I still had my account, because some of the sites look very good and they are not very expensive.
I hope this article will help you in some small way if you are considering building Adsense sites.
Good Luck!
Clint Pollard has been marketing on the Internet for nine years. You can find his top Adsense recommendation at Adsense Ready. http://adsenseready.ncave.com