Up to now I aimed to maximize the Repairs and Supplies categories of my Schedule E, to make sure I have as large a deduction as possible.  

Not to say that weeks before the semester starts you can't get tenants but tenants look well in advance and if you don't secure someone  well before the semester starts you  can run into trouble filling the unit for the year with students,  depending on the area supply of course.

It could be the water supply line dripping on to the floor.

Some things to be mindful of are the added costs of having to facilitate delivery and acceptance of the windows if you are purchasing them yourself rather than go through a contractor who both supplies and installs the windows.

Or at a local real estate meet-up is another great option.3) IMO (duplex, triplex, quadplex) are best, butttt in some areas supply is limited.

Our plumber re-plumbs entire houses for much less than that, and if it's a simple leak you can find, you could be done for a few bucks.The 80's were the era of pinhole copper, so there's always a chance that your supply lines are shot when buying a house from that time period, but it could be something minor too.

Higher than inflation appreciation will occur where demand outstrips significantly supply. 

While I don't supply paper towels, each of the three bathrooms is stocked with three rolls of toilet paper.

Phoenix, AZ has been a great market for the past 10 years, but not so much in the past two years, as supply has really started to inhibit price and rent growth.

They need to connect with one anther and to the unit supplying them.