I'd guestimate that almost .25 of Fountain Square is STR.

If it was me...I'd check with zoning to find out how many dwelling units I could build, and I'd find what the requirements are for those units (type of house, height and setback restrictions, etc.).Then I'd find out what local builders think the cost to construct would be - just get a cost estimate per square foot for 2 or 3 different levels of finish.

The ones who bought cheaper properties trying to fix up had mixed results with one getting hustled by a contractor and definitely going into the red.

Because that can be a red flag.  

Even you got hung up on the HELOC red herring.

Spanning more than 8,000 square feet, this outlet will feature a large outdoor patio overlooking the Strip and a unique company store selling exclusive merchandise alongside your favorite burgers.

I started out with value add, where we force appreciated properties by adding square footage and beds/baths.

Not calculating maintenance expense could end up being a nightmare.I always estimate (using either the 50%, 1% or square footage rule) the annual maintenance / first year of maintenance fees for a ALL rental property.

After some investments in amenities (primarily hot tubs), our last 3 months have averaged 12k/m.This property is owned outright, and due to the size of the property, the small square footage of the units, and the lack of comps in the area we have found it difficult to lock down any refinancing.

Computers can analyze property based on subjective data (square footage, # of beds/baths, etc.) but cannot calculate for objective data (quality of kitchen cabinets/counters, size of bedrooms and bathrooms, view out the living room window, etc.).You should study the market yourself.