As for the hot water tank / HVAC pans, it depends, not required that I know of, but if you want one you can go buy it and have anyone install it, just lift the unit up and slide it under.

Hit water tank vent pipe is disconnected.

I went off " Of course utilities are included , we pay all your electric , pay per view cable , I restock your refrigerator and food once a week , I wash and fold your laundry , and i will even fill up your gas tank every week . " There was a short bit of silence ...............

When did you decide to tap the fish tank? 

Short version from me this time, rents tanked in Silicon Valley when I was managing a 25 unit building.2.

Each mobile home has a separate address, no sewer due to the septic tank, garbage is taken care of by city.

You want to increase value, not tank a neighborhoods appraisals.

I occasionally had to light pilot lights or he had to clean out the tanks, but it was really minimal maintenance.

This was a fish tank that got moved in and woops, the tank sprang a leak in the move. 

If the market tanks, you hold onto it and keep collecting rent.