Rainwater arrives on location, cost-free, and pure && You can turn poop into valuable manure through composting :: 0 fuel costs, 0 waste, 0 overly complex machines with 0 "exciting business models".
California already has a massive system of rain water capture and extra-large cisterns we call reservoirs. The smaller the cistern the more expensive per gallon it is.
Your approach is fine for a rural compound, but doesn't scale for urban environments.