Basically I will keep his stuff until he pays me a storage fee of $50 a month. 

The owner has his book keeper for his storage business do the books.

Does this mean I can just leave it off for good...or better yet, remove the HWH and free up some storage space?

There is no basement, the ground level is not habitual and is used as storage, and the 2nd level is a 1 bedroom.

There have been enough improvements in storage tank heaters in the past decade that your new heater will consume less energy than your old; perhaps significantly so.

The rest being unheated storage, garage/workshop, loading dock (yep, that's right) and an open-on-the-end car port.

Maybe as additional rentable space much like parking or storage? 

@Alberto Stein RiosYou are not likely going to find a credit vendor who will allow you to pull any type of credit without brick and mortar along with policies to protect the reports including storage and destruction.  

Kind of like what you might see in a storage room, garage, or workshop.Even if the wiring is up to the code and passes muster, I would be concerned about the aesthetic issue that may turn off potential tenants.The bigger issue here is the use of an FHA loan for a rental property.

I've thought about finding someone local who likes to re-sell old stuff (like someone who buys storage units.)