Looking like I have a lot of drywall to hang tape and mud in the near future

I generally figure about $500/bedroom for these things.Obviously this is much more shoot from the hip than what Paul uses, but I guess that's because it's variable in my case, due to the fact that rental properties come ready to rent.I therefore try to hit the ground running with a rental and then work on updates over the shoulder/mud seasons (May and October).I guess my point is that your calculator sounds interesting, and looking to include FFE calculations is probably a good idea, but make sure it's optional for cases where it's not necessary.

It’s a method to sell otherwise undesirable houses In  Sketchy areas to the locals that can’t get  traditional  loans .

We've seen plenty of good plans never come to fruition because the developers failed to obtain buy in from government (MUD/other utility/city/county/state) AND the neighbors! 

Without it you are stuck in the mud. try some local mortgage brokers.

I would then use Trulia's crime heat map function to filter out any 'undesirable' areas as well.  

In no way was I implying the tenants of these properties were bad people, simply that when I tour the property and talk to them there are extenuating circumstances and strange deals with the current landlord that have allowed them to modify the property and use it in undesirable ways. 

To get 12 -15% in today's low interest rate environment requires one of three variables (1) work the note - usually a non or sub preforming note or (2) accept a higher risk, i.e, second lien position, very high LTV, borrower with very low credit scores or bad credit history, D property in undesirable areas, etc, or (C) get VERY lucky!

Is it really a ghetto or just a slang term you're using to describe an undesirable area?

With your current specs you will most likely find yourself in some of the most undesirable neighborhoods and ultimately not find very good cashflow.