(A slab or water main leak) but it could also be as simple as a leaking toilet flapper. 

@Vamsi Pan you would have $1M if it sold?

What repairs will be done(clogged toilet, burner not working, hvac service, etc).

I did all of the renovations on the first half of my duplex (replaced flooring, subfloor replacement under toilet, toilet replacement, counters, sink, backsplash, paint).

Look under sinks and around toilets and tubs for signs of water leaks.

One flush or two flush toilets??

Anything longer requires Landlord approval in advance. 12 days every month is too long.At a minimum, I would tell her that the utilities are included for her, not for a guest that hangs out when she's not home, washes laundry, showers, cooks, uses the toilet, watches TV, etc.

The trailer is 21 ft. long and has a built in full bathroom with a shower, toilet and sink.

Same with toilet flappers,  clogged traps, etc. 

They will have a better grasp on the market than a realtor in terms of how these properties perform.When calculating expenses make sure to account for property management, electric, water, gas, cable, internet, cleaning, lawn maintenance, propane refills, toilet paper, paper towels, coffee, shampoo, etc.