I have a locked privacy fence placed between the main house and the in-law suite, and separate yard entrances for them, so I am trying to provide maximum privacy. 

Common entrances should be locked. 

It has a common entrance with four one room with private bath on main floor and four one room with private bath upstairs.

Know your exit before you execute your entrance...or this will become a "shiny object of distraction" and bury you faster than you can say, "...it looked good at the time".

I just got my license and now I want to know what the first step is to making an entrance into the real estate INVESTING side of the business.

Also, seal the ant entrances to the domicile and use a good perimeter spray product.Inform the tenant that effective pest control takes a team effort and that it can take some time to eliminate the problem.

I could have the studio portion of the property (now functioning as the living room/kitchen) maintain its shared entrance with another unit in the property.

:)   L/O is both an entrance and an exit strategy."

The thermostat is currently in the hallway right near the door entrance of the building in the common area.  

I just put some flooring down in my home and cracks are typical.Take a look at the windows and door entrances for foundation issues.