Users get a "pro account", much like the Twitter Verified badge (called lolipop AWESOME) for a week if they "Download a free app". Those pays everything from 20 cent to couple of bucks per download.

App runs barely any hosting cost, and this generates a nice little passive income. I have an admin panel to turn on more ads, but as of now I would rather grow with as little intrusive ads as possible. When, and if I turn on more intrusive ads, users can purchase a "pro badge" to get rid of ads. (turned off now).

Best side effect is that I have gotten a LOT better at obj-c development since I started playing with it, and now run a small mobile development company that actually pays the bills. Learn while you play :)

This is awesome! I'm teaching myself Obj-c now and would like one day to take it further. Glad to hear that it's working out for you :)

Best of luck :) If you have any questions, be sure to ask. I started with the Stanford videos on iTunes u. High quality stuff!