Joe, of Homesteadonomics, who is located out in Arizona has done a really nice job of designing, installing and living off a rainwater harvesting system for he and his family. This video gives a detailed tour of his system. The following video is a Q and A on his system.
Granbury, Texas where Texas Tiny Homes is planning to build some small luxury homes averages around 35" inches of rainfall each year. Adding a rain-harvest system to supply the water needs for our homes is something I believe is possible, but have not sat down with the county health department to confirm that. I like the concept and will be exploring the possibilities, designing a workable system and its pricing.