The blogging service Hubpages offers an easy way to setup a blog, add adsense to it, and make a profit.

Creating the Blog
I created a blog with Hubpages as a test. The whole process was incredibly easy. They will ask you information pertaining to the blog that you want to write, and they will setup the rest.

Adsense Already Installed
With Hubpages that Adsense Banners are already installed for you. They keep however a small portion of your profits, 40%. However, according to Hubpages: HubPages is a highly-trafficked site, and because you’re publishing high-quality content, you’re going to find plenty of readers. Plenty of readers = Plenty of Adsense clicks.

I can’t say I recommend Hubpages due to the fact that they take some of your Adsense profits, but if you want to be a freelance writer this is a good place to start.