With the concept proven, it was time to actually spend some money to build a foundation. These cinderblocks were $0.87 each. The strange burial pattern is to level out a slight slope, and the uneven spacing of the blocks is to dodge the root of our neighbor's Pepper tree.
Since the boxes are untreated mild steel, they need some kind of paint. And since the previous owners of our house had terrible taste, they left us gallons of paint in rose and various shades of beige. The bottom of the box, and the two sides that face the back of the garage and the fence, then, used this free paint. The rest was painted with free exterior house paint left over from our house's recent paint-to-sell job.
To illustrate just how light this corrugated steel is, this box was screwed together three high in the middle of the yard, and then moved into place fully assembled by simply sliding two 2x4s under it and having one out-of-shape engineer lift from either side. (The long ears on the top level were a result of the wrong size boxes getting thrown away. The extra material was cut off and the top level was shortened with only minimal bloodshed.)
Since the panels have almost no torsional rigidity, the big open doorway leads to the shed bulging outward where the panels are unsupported. The door needed to be framed with something that could hold the corrugated steel upright and straight. Amazingly, the same dumpster that provided the steel also provided this 12-foot long 2×10 that I placed across the top of the opening. After spending about $5 on the 2x4s you see here, the door was framed and the shed suddenly had the structural rigidity necessary to hold my rakes and paintbrushes.
Now the big spending begins. A few more 2x4s and some corrugated fiberglass from the actual pay-for-stuff-with-money store and the shipping crates start resembling an actual building.