Don't forget the cost of renovation, furnishing the house, and the amount of time you spend answering calls, booking stays, dealing with problems, cleaning, or whatever else is involved.It seems like a lot of money to spend for that kind of income. 

I have a contract with an HVAC company that comes and cleans/checks out my units twice a year; typically at the beginning of "heat" season and the beginning of "cooling" season. 

NOT ALWAYS  2008 to 2012 cleaned many SMART investors clocks  with billion dollar development and syndicators going busto .in a crash for sure those with Cash  and not afraid to pull the trigger will do well.. 

electric on or not?

Are you adding in realtor fees and also holding costs like insurance, electric, taxes, water and garbage?

Currently there are trees from a next door property that has grown over a fence into my yard and and even grown within the electrical pole wires (dangerous) Whose responsibility is it to cut them back?

A couple of young ladies have been renting for 3 years and they are ideal tenants (they always pay on time, keep the apartment neat and clean, very reasonable with all requests etc.).

Include attorney fees, carrying costs and clean up expense.

Specifically around showing the property or cleaning between tenants? 

You could offer to be their eyes and ears, deliver materials to job sites, run errands, clean up a job site each night, etc.