Though you would not need footings that deep, I would strongly encourage either cement (my preference) or galvanized steel footings and then simply build your fence using pressure treated wood.

Some installers insist on using fix-all instead of a mortar or Portland cement because they say the alkaline of the cement product will erode the fiberglass.

They're fitted together with cement, as in portland cement and sand.

Have you looked into cement?  

It is all surrounded and covered with gravel and the floor is re-cemented.  

Mostly depending on what finishes are selected...vinyl siding, cement board siding, brick siding?

The carport cement driveway needs some work.

Should I look at multi family units or single family units with a cement foundation?  

I would really like to update my SFR and put in a new railing around the porch since the current enclosure is rusting out but the fencing is cemented into the porch. can I remove the railings without damaging the porch or do I need to replaced the entire porch to cement new railings?

The prep process was very labor intensive (knocking down high spots with a sander, filling in large cracks/gaps/gouges with cement filler, containing all the concrete dust from sanding) and laying it down took several days of fairly difficult and slightly messy work.