The referenced post has been removed.
Not everybody lives in an area where that much stuff can be salvaged. Honestly for how cheap 2x4's are I'd rather just buy them unless I specifically new of a place I could get them for free. PVC is dirt cheap as well.
It's one thing if you literally have no money but you can build a decent setup for cheap if you do it right.
If you can find some decent sized plywood scraps that would be clutch as plywood isn't cheap.
I personally would rather just drop a few bucks than spend a whole summer driving around trying to find enough scraps.
I'm not arguing again doing it just making it seem the most viable option. If it's available use it all. If it's not I think it's better to built the thing and shred it than worry about finding stuff.