Today, I have acquired two dozen Android phones with 2gb+ of ram, and 16gb storage, for free. I will be using these in a weather resistant box, powered by deep cycle batteries and a 40watt solar panel. This should allow the devices to remain on without costing any money.
Each device will be mining Monero at 18 H/s, for a total hash rate of 216 H/s.
This cluster will generate approximately $78 USD per year.
If I can manage to create several more clusters, I'm sure I can have them up and running on multiple sites without costing me a dime. It'll be pure profit from day one as I have all the material, and will be obtaining the Android devices for free.
Wish me luck, and comment your opinion or some tips if you've attempted such a project before.