My husband and I currently reside in Mount Pleasant, South Carolina.  

Each is about the size of a large plastic container or shopping cart, and they mount right to the wall.

i get one of those mechanical lock boxes from masterlock and mount it to a post or the deck, in the event that the smartlock fails i can get them a phsyical key from the lockbox by giving them that code.

I replaced a broken railing mount for the interior stairs because a guest noticed it was cracked.The bottom line is to setup processes for yourself (or handy person/inspector) to go over your rentals a couple of times a year. 

Are these ground-mount system or roof-mount? 

A bit about the land: it’s in a neighborhood located in a national forest about 40 minutes from a bustling and growing city (Mount Pleasant, SC).

@Nick BrittonRight now the focus is the Mount Snow area in West Dover.

For the money you will pay to invest on the 1600 block of N 27th street, you are better off buying in Germantown/East Mount Airy where the fundamentals are better or spending more to be in a better neighborhood.

While quality work is not mutually exclusive to adding more features to a property, I have seen a lit of flippers houses that seem to do just that: add a hot tub, but can't seem to mount a toilet securely to the floor, or leave the 20 yr old furnace.

Bottom line a roofing company isn't going to typically pay for punctures to the membrane of the roof like a roof mounted a/c unit.