As of today I own 13 doors; 3 of them UD student rentals and the rest in Wilmington.

You opened the front door by unlocking it and then pulling a rope that lifted a lever inside.   

Also measure the profit per door and fix or sell the dogs.

I would warn you though as soon as you give an inch, the next month if rent is not paid on time you may have opened up a door of forgiveness that was not intentional.

Painting, plastering, refitting out fixtures and fittings, windows and doors.

Do you by chance have it written anywhere to close all doors and windows? 

I sent her a 5 day notice via certified mail with return receipt requested because she wouldn't answer the door or answer my phone.

You've listed the "big three", and those are all that are needed for most MTRs, especially if you have a limited number of doors in an area.

Maryland is one of only a handful of states that does not require Property Managers to have a license from the Real Estate Commission, although it is optional.Also, selfish plug, I am fully licensed and run Blue Door Residential Property Management and am happy to speak with you.

@Andreas Mathews admirable, but make sure you do some research so you understand what a PM can make.Starting your own PMC business will require 75-150 doors to make a decent living, depending on gross rents and your fee structre.Working for a SFR PMC as a PM, will require a RE license and you usually get paid a percentage of the gross rents the portfolio of owners/properties you manage generates.