well, you will have to boil a bale of hay in a 55 gallon drum, then
spawn it. You can just wet a bale of hay, and grow bacteria instead.
But you could also buy 1000 plugs and with them spawn a ton or so of
freshly cut logs (not so freshly cut, you have to wait about one month
so that their fungicides dissipate). Then for $20 you would have quite
a bit of mushrooms for years to come. if you have stumps in the shade,
you could inoculate those, and then you'd get mushrooms for many years,
but I should warn you that my stumps never made it. About 50% of my
logs do produce.