Do the guys next door melt stuff? Because if they pour into greensand, your casings possibilities are huge If you are into old machinery, some missing parts are made of pure unobtainium.
Just looking at the stock… there is enough square column to host a tire hammer build for the smithing enthusiasts. The scrap yard near me goes from okay to the owner flying off in rages in an instant. Did I see two machine shops on the corner?
Casting is something I am in the process of working on…getting the waste oil furnace to a more friendly startup and depending on the fuel jet I put it the btus are more than enough for any casting, forging, etc. I need to work on crucible, holders for this process. Between our 3D printing capabilities along with being able to cast it would be awesome!
There is an honest to goodness bell foundry near me. They discard their casting media after one go, being as the bells are kinda gotta be right first time kinda casts. Anyway, I have thought mulled, that might be a fine start for greensand, which is essentially bentonite and sand. IF I recall of course, been a while since I looked at casting. Bentonite can be bought in bulk at drilling companies. Environmental companies use the stuff to seal monitoring wells. Odds are that can be gathered up on the cheap. Who would of thought good old snotty bentonite clay would be so versatile? Man o man, had I known… I would have saved gobs of it all those years ago 
If we can find a caster that will pour partials of leftover runs, maybe cheap castings? Dunno.
Depending on what you are casting with, an old fire extinguisher makes a really good crucible. That was my plan for my castings, but then, I’d plan on casting with aluminum or zinc.
You can make ceramic crucibles that are functional, but don’t have the lifespan of a commercially processed crucible.