Examples to kick it off: adding solar panels, vending machines, advertising space, allowing credit card rent payments w/ fee. 

LTR, STR, MTR, BRRRR, Multi-Family, Businesses, Cash Vending, Note trading, Tax Liens, etc. 

A lot of things are not used in store. 2 coin machines, 1 is broken and could be replaced by a card reader, large vending machine empty, soap vending machine coins could be converted to card.

I know people making $20k+ months couch flipping and investing in vending machines.

FX, Crypto, Flipping Houses, Sub2, Gold and Silver, Rare Earth Metals, Day Trading, Bernie Madoff, Vending Machines, Car Washes, Amway, any MLM.....whatever the dream of the day is.In all of them, you can make money, you can get rich, but almost always it takes a lot of hard work, blood, sweat, tears, missed holidays, working on weekends, money, risk, stress.

Back when I was brokering commercial real estate 100 years ago I had a deal on a small office building fall through when during the walk thru just prior to closing the buyer insisted on checking the candy vending machine and verbally to;d us and sent us a follow up letter informing us that he wasn’t going to close because the Baby Ruth’s in the candy machine were stale.  

You could install vending machines.

Vending machines as well  It uses an App and the Bluetooth on their phone so you don’t need WIFi. 

Value add: We look for ways to add value to the property, such as a laundry room/machines (electronic, no cash), vending, adding water metering under our new leases, etc.If it doesn't work, it doesn't work.

The ice machine/vending machine lobby has a camera, the 2nd,3rd,4th floor elevator lobby has a camera.