grow mushrooms.
they take up much less space, and can be grown in small buildings or tents even. plus i think their demand, especially exotics and healthy kinds, is on the rise in the western world.
another minimal space alternative is micro greens. again, can be grown in a small building, tents, or greenhouses, and good demand from growing healthy trends (at least in the west, i.e. u.s.)
also, if you do it right, i think both of these crops can be relatively good earners as margins can be increased if you go about setting things up properly.