Basic landlord tools should include a lot of the above, but also a toilet auger (one that has the plastic sleeve to prevent scratching porcelain).

Some examples of reasons they have called: they broke the handle off of the hot water nozzle in the tub (three times), they saw an ant, they saw a centipede, they broke the toilet paper holder, they asked us to install a new handle on the stove, they couldn't get a window open, they discovered old paint on several of the outlets in the house and asked that I replace them all.

Students will tend to skip after graduation or at end of school year if roommates or school didn't pan out.  

Such as a fridge, oven, cabinets, toilets, etc.

I was renting a room in a house when the toilet in the restroom next to my room overflowed (not at my fault) and flooded half of my room.

We filled up 3 55-gallon drums of water for things like flushing toilets, washing dishes, cleaning themselves, etc.  

In addition to what @Deanna McCormick and @Kyle Doney have to say, I would say this is the perfect opportunity to not only get the #2 unit in shape, but improve it so it has what a senior needs to age in place..... comfort height toilet, bathroom grab bars, handrail for steps and/or ramp, doorways wide enough for a walker, great lighting, smooth flooring (either wood/vinyl or very low pile carpet) and no throw rugs.

One told us to move a gas hot water heater ($1200), then the other said we had to recertify the chimney liner, change the vent, and add a special drain line to the black catch basin rubberized pan under the heater ($1000 more) because somehow standing water in the pan with a water alarm wouldn't be obvious that the hot water heater was leaking.In shows like Flip or Flop you can watch where whole additions have to be demolished or all the drywall / tile removed to take the construction back to the framing stage / open electrical / plumbing for thorough inspection.

For what it's worth, it does mean you have to worry about those toilet seals.

Your credit is already in the toilet you do not want to completely flush it at this point.