I take as close a comparable property as I can (style, size, #bedrooms/Bathrooms, location, etc) that has been sold and make adjustments based on the condition as it relates to the property I am trying to valuate. 

Now I just did a complete rebuild on a Chicago style porch, and that is a different story.

The comps were  are Up/Down or Front/Back style duplexs'. 

NC has no rent control and long term tenants are not that hard to find since people are moving from bigger cities to more relax wfh life styles.  

IMO you can go out an easy 45 mins and find plenty of options, then it all depends on buyer preference regarding size, shape, style, $ etc... 

I’m interested in a single family home that currently has 2 separate “studio” style apartments within the home.

As mentioned above, you'll need a commercial loan....meaning, you cannot use a conventional loan or FHA style loan on any property 5+ units. 

LOL) and pessary shut off valves and new plumbing - kitchen etc. new fixtures with the new sinks, new soft close cabinets in kitchen and large stainless chief style sink with custom granite counter tops.

The most common portfolio style loan in Texas is a 20 year adjustable rate loan.

I would also take this as an opportunity to see what the styles are in that area for the house to rent on Airbnb in your area.