Consider calling around to local GC's. They are used all over on jobsites and office yards and they get turned over every so often. They are usually structurally sound but can't take the constant transportation loads (offloading/reloading, etc.). And for a larger company, the value is in buying a new one rather than constantly tending to an older one. They can usually be had for a good price if you're willing to wait on them to come available.