I have been told that to convert an already existing window to a sliding door, I will be required to get my adjacent neighbor's signature.

As an Engineer, I wrote a Windows application that keeps track of the property information that I have inquired about to follow up later and just because its fun to write an application.5.

NEW thermopane windows throughout.

NEW thermopane windows throughout.

We wanted to sell that property within the window of living there 2 of the last five to avoid capital gains, and move that equity into cash reserves and other real estate projects in the Denver Metro area. 

Does your lease have guidelines of good behavior (like no laundry on the fence, or foil on the windows?)

One of my clients did this in Pinellas County.As for getting the unpermitted work, permitted and approved with the building department, this is reasonably common and not a difficult task.

What do you know about the condition of CapEx things (roods, windows, siding, pavement, structural) will they make it for 5 years? 

If the property other than the HVAC isn't a disaster then I would be an advocate for getting a second HVAC and thermostat put in as well as separating the meters. 

In summary : Become clear on your reason for getting into real estate investing.