She then got a message from the tenant yesterday that said: "I know the plumber came but we did not have hot water yesterday and again this morning.

From our experience, when flipping properties the most efficient ways to spend your money are the following:Focus on kitchens and bathrooms, as these areas consistently provide the most value for your investment.

If you have class C rentals, I like to use Traffic master Grip Strip Water Resistant Luxury Vinyl Plank Flooring.

This means, no electricity and no water as the well can't pump - which also translates to you get one more flush on each toilet and then you are done.  

They know the tenant base, median rents of different areas, how much to increase rent each year, ranges of repair costs (ex: tenant calls and says AC isn't working, no hot water, faucet is leaking, the HVAC system goes out).

Including Water in Rent: Another option is to adjust the rent for each unit to include the cost of water.

To manage this, find the average electricity, water, and gas usage in your area.

Not efficient management. 

Maybe find out you didn't replace cathodes, and the water is harder there.

But in all cases I would argue time is the most precious commodity to invest, and it's invested most efficiently through focus, so look at those two the most carefully.