If you're looking for a simple way to set up ads on your android app for income, check out http://www.mobfox.com/?aid=14258 (my:MobFox) . I've been using it for a couple months now and it works well.. You can set up the minimum amounts that you will accept to display ads and for ad clicks.
Setup is pretty straight forward all you have to do is download the jar file.. include it in your eclipse project.. place one xml tag in your layout, and, viola.. you have ads on your app.
From there, just get as many downloads as you can and keep your content good.. The app will make money for you and you can offer it free to the public.
Try it out and reply to this thread for help.. I will be subscribed.