I have a friend in NM that collects rain water in two 1500 gallon tanks and uses that in her greenhouse.
Those, suprisingly, are fairly inexpensive for the amount of water they store and their projected lifetime. And they protect the water from contaminiation.
/johnny
I bought an 1100 gallon black polypropylene agricultural tank 3 years ago and put it under the rather large deck we were building at the time. Piped a couple of gutter downspouts into it and use it for irrigation water, with the idea that with a good filter I could use it for drinking water in an emergency. We were in a declared drought at the time, so outdoor water use was severely curtailed, and I wanted to make sure I had water available for all the new back yard plantings associated with the project. That Fall, the skies opened up, the lakes filled, the drought ended, along with the outdoor water use restrictions. Still glad I have the tank, it saves me a little money on irrigation, and there’s the prepper aspect to having it there.
I wish I had gotten the 1500 gallon one that was the same diameter but a tad taller. We were having a little trouble getting it on the trailer I had rented, but I think we could have with a little finagling. It would have still worked with my deck height and the horizontal piping fall (one of the downspouts is about 45’ away).