I know someone who minimally rehabs old shacks on the cheap and flips them to eek out a living.

One of his favorite materials for cheap roof underlayment moisture barriers is disused vinyl billboards.

I wonder if any of them will survive long enough to be a similarly interesting artefact when next replaced. They often get corrugated metal over them, in a dry desert environment I can imagine metal roofing lasting well past 50 years.