Converting Quadplex into Two Duplexes

[Sarah Mariscal]

I own a flat roof quadplex which consists of two single-level duplexes side by side located in Jacksonville, FL. 

One side needs re-roofing and it's being recommended by various roofers to have a pitched roof rather than a flat roof. 

When I first purchased the property years ago, I had it in mind that eventually I would want to build a 2nd level. Most quadplexes in the area have two stories (2 on 2). I never got around to it because of some roadblocks:

1) I was told if I add a 2nd level, I would exceed 1-4 multifamily loan and would require a commercial loan. Can anyone elaborate on what this process entails? I have an existing mortgage on the property. 

2) How does one obtain financing for such a construction job? Do you get the loan first, or get the loan/finance through the contractor first?

3) If in the event zoning is an issue, or it makes more financial sense to not convert to a commercial loan, is there a way to SPLIT the quadplex so that each duplex sits in its own lot and I become the owner of two separate lots, each with one flat roof duplex? Then I can simply build on each of these duplexes and have two quadplexes. 

Thank you all for your time and knowledge!

If anyone has any roofers, contractors, handymen they recommend in Jackonsville, FL by all means send them my way as well.