DIY

One or two crops usually per substrate container, but then you can just refill the bucket with new substrate. The smallest usable container I had was 1-liter milk packages - I just filled them with a straw/manure mix straight from my horse stable and pressure-cooked them (my pot fits about 6 of them). Then I take them into my still air box to add grain spawn. Close them and leave them for about a month. Check if they are all filled with mycelium and smell shroomy, cut two corners of the milk box and keep in a humid environment (can be a large plastic box regularly sprayed with water or a shower cabin with a humidifier). Then it takes about another week to grow mushrooms. I did this with pink oysters because they are quite forgiving about my DIY setup and had a regular small supply of shrooms to add to my food.

I guess that would the smallest workable setup, but it does take regular work to fill these little packages, and ultimately I've had too little time to keep this up among other farm duties - wild mushrooms will be out soon and hunting for them outside is just way nicer than boiling straw and shit indoors. I might make it a seasonal thing as well because finding the right temperature can be difficult throughout the year (some rooms too hot in summer, some too cold in winter), and mycelium can be kept over months in a liquid culture or on agar in the fridge.