I have a few [1] Android Apps that bring home around £90 a month. Ironically, the ads from one app (I don't like ads as a business model that much) make as much as the other 4 combined.

I also wrote a book [2] about game development in Haxe, and self-published it on gumroad. That brings anything from £40 to £150 a month.

[1]https://play.google.com/store/apps/developer?id=leoncvlt&hl=... [2] http://discover-haxeflixel.com/