More details about your
water need, and your
land situation, would help with suggestions. Usually the cheapest way to collect water is using
earthworks, but that isn't much good on a
city lot, for example...
If you need to stick with roof collection, and you're near a city/town, and able to watch closely and respond fast, your cheapest option of all would be to snag a free shed or 3 off craigslist or the
local alternative. I've seen a few pass by here, but they go *very* quick in my area.
I've built a tool-shelter out of an old pickup
canopy with four tall fenceposts and a couple
pallets; it could be angled to mostly drain into a barrel if desired. Quick, crude, ugly, but the fibreglass/aluminum canopy will last ages, and very cheap to do. Canopies are much easier to get for free than sheds.
