I was actually thinking of cutting the cans open and flattening them to make large 7″ by 19″ steel shingles. Then my wife, Julia, suggested I use the top and bottom as shingles like you describe in the eves. Crazy cool idea huh?

I suspect local restaurants, like pizza places, would hold cans for me. Back in college I worked in a lot of pizza places and we went through dozens of #10 cans a day.

I think I’d need about 220 of them for the roof.

You could get all your friends and family to take off the tops and bottoms of cans to give to you and recycle the rest.

They would already be fairly flat and uniform in shape.

EDAR (Everyone Deserves A Roof) is a 501(c)(3) charity that provides unique mobile shelters to those living on the streets all around us. Each EDAR is a four-wheeled mobile unit which carries belongings and facilitates recycling during the day and which unfolds into a special, framed tent-like sleeping enclosure with a bed at night.
http://www.edar.org/