Most people think farming means land. One grower did more than $150,000 a year out of a room the size of a parking space, selling greens by the tray to restaurants that reorder every week. Here's why revenue per square foot beats acreage.

A commercial airline pilot bought a five-acre worm farm and turned dairy manure into soil that sells for hundreds of dollars a cubic yard. His customers are Napa vineyards. The feedstock is often free.

A restaurant kitchen sits idle for hours between rushes. A virtual restaurant brand fills that dead time by cooking under a second name that exists only on the delivery apps. Same fryer, same staff, a new stream of orders.