There's a learning curve with tenants who have a hard time figuring out the machine, so you'd have to train your tenants or field calls asking what to do.And what I don't like about them as a tenant, is that they require a minimum transfer of funds from your bank account of $10.  

If you can solidfy a well-oil machine for getting units rented, and subsequently turned over in the summer time for next year, you can have a very profitable business.College housing usually starts marketing their rentals in first weeks of the spring semester, with leases starting in the summer/fall!

@Ginny WatsonYou may want to try an ozone machine as well.

But in March the upstairs tenant calls us again and says that her washing machine is not working.

The Japanese are awesome at creating a lean mean machine for every type of company out there. 

By having curb appealPlants on the inside of houseAroma Machines – smell of baked apples or home cookingClean and prettyc.What color of paint should you paint your rentals.Basically white or off white.

Treat it like a washing machine.

off topic: in one of my buildings (88 units) i bought a key machine and my onsite manager make extra keys. 

@Taylor Comer I second the advice about Google voice - free and super useful - you can forward it to your cell, have it be just on answering machine, customize greetings, etc. when the number gets called both my phone and my wife's phone ring and when a message is left I get a text and an email transcript.

Never had a fire, just went with the green machine ideas.