You could also let each new property pay back the money you borrowed against this one to eventually pay the HELOC back down.If you are looking to really go for it and get into commercial/ apartments I would sell this and go for the 1031 as suggested by @Caleb Heimsoth.

This is considered a commercial property (5 plus units).  

Or perhaps you could get a commercial bank loan and have the seller carry 30%? 

Background: I have a Florida real estate brokerage company (an LLC that has elected to be taxed as an  S-corp) that is 100% commercial real estate focused.

I would also look at its access and paring. 

-the community is gated, close access to I-35, and will have at least 90 units.

If you do have the funds, and want to do some of the work like installing flooring, painting, etc. yourself, I would skip the renovation loan and additional requirements that come with it and keep things simple.If you don't have access to additional funds and don't have the ability or desire to work on the property yourself, and the property won't qualify for regular financing without some of the repairs, then I would definitely recommend the 203(k) loan.

Second, and perhaps most importantly, it's land-locked behind another property, so I don't even know if any buyers would even have access.

Crime rTes are important as well as accessibility to highways and shopping.

I grew up in Altamonte Springs ('87-04)  and saw it go from a rural town to what it is today, sort of a haphazard mix of nice residential, not so nice residential, run down commercial with pockets of freshly built/rehabbed commercial, low income apartments-turned condos before the crash-turned foreclosure havens that are barely recovering....