Well, for the tank ferrocement is relatively inexpensive if you have the workers needed for the size of tank you want, although cement is not very environmentally friendly. Constructing a Ferrocement Tank is a good place to start learning about this option. Although pvc is the cheap easy material for household pipe, I believe water tanks and irrigation pipe use polypropylene or polyethylene rather than pvc; not sure if that distinction makes a difference. I've read about inexpensive water tanks using EPDM pond liners contained within chain link fence reinforced with steel cable hoops, but I can't find a link.
I'm in the foothills of the San Pedro Mountains in northern New Mexico--at 7600' with about 15" of precipitation, zone 4b historically--growing vegetables for the local farmer's market, working at season-extension, looking to use more permaculture techniques and join with other people around here to start and grow for farmers markets.
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montana community seeking 20 people who are gardeners or want to be gardeners