It is extremely hard to be profitable at growing mushrooms, but if you can align your business to your communities needs it can work out. Scale and target clientele are going to be the deciding factors. I've worked with multiple mushroom growing businesses as an architect and also in operations.
One of the first things you need to figure out is who you're selling to. Do you have contacts in restaurants? Can you get into local grocers? Are you aiming at the farmers market? Or do you plan on selling through a digital platform? Next, what square footage can you get. The biggest job of growing mushrooms is storing myceliated substrate. You'll need a clean room, an excellent HVAC system with extensive FAI and a humidifier, and lots and lots of storage space. Also, the amount of compost you will generate is substantial.
There are strategies like selling the myceliated blocks after they're colonized directly to consumers, which takes care of you storage and fruiting and shelf life problems, but that's not exactly selling mushrooms.
Not meant to discourage you at all, growing mushrooms is absolutely rewarding all on it's own. If you are planning on diving in however, you need to put together a solid business plan, not ask random folks on a building code forum.
DM me if you want more info.
