I have 1200 square feet and it seems about the right size with a touch of room to grow. I could certainly squeeze into a small space - maybe 800 sq feet but man I don't think I would want to. Green Storage, roaster, tables for packaging, brewers, sinks, bathroom, office space... it all adds up fast! Im really glad I made a dedicated cupping table and allocated space. I cup WAY more than I ever thought I would.
Just for reference... I'm a few months into business, wholesale focused and operating out of a shared industrial space (small bays). One thing I ran into in my town.. is that most nice clean industrial spaces didn't get much less than a 1000 sq ft. Certainly you can find some oddball spaces but you have to consider the amount of capital you will spend getting the spot up and running (exhaust / plumbing / electrical / AC)...