Another good one is RV storage areas. You need what amounts to a carport (roof, cover, something), electrical hookups, security fencing, cameras/security people, and sometimes you can even get away with minimal paving. Around here you can charge $2-500/space/month. That adds up pretty fast in a good sized lot, and TONS of people bought RV's for the prepper days that were obviously coming during COVID.
There's more downside risk compared to mini-storage as the economy gets worse IMO, but not all that much and if anything it's even less infrastructure needed than storage if you go barebones.