In Seattle, we have a paper called the Little Nickel which is kind of a newspring flea market of want ads and for sale ads. They always have ads for "pole barns constructed on your level lot" or "detached garages built on your slab" etc. Look around in your area, and you should be able to find a similar paper that advertises these kinds of things.
I made $1000 on a bunch of carpet I tore out of a house a couple of years ago. I sold it in the little nickel and the buyer came and hauled it away on their own. They were thrilled, because they got it for about $8/yard (it was close to $18 new and it hadn't been used due to forclosures after construction), and the sale saved me having to pay to dump it! Only in America!