Additional Income Streams for Rental Properties

[Via Krishnan]

Hello BP Folks,

As the interest rates rise, we are all seeing downward pressure on cash flow. To address that, I am exploring additional income streams that will boost income for my properties. 

These are the specific ideas I am thinking about now:

1. Solar (to reduce utility)

2. Inline water meter for every unit (to reduce utility)

3. ATM Machine (inside the property or facing the street - street has more foot traffic)

4. Vending Machines (inside the property or facing the street - street has more foot traffic)

What do you think about these above ideas? 

Most importantly Any other opportunities to generate Additional Income Streams?