The numbers may be great but you need to understand the headache factor involved for you if self manage or how much it would cost you for a property manager to handle.  

Mentioned a great point, the tax consequence of a sale will bring property tax up to date based off the sale and the last time it was accessed was when the park was built in 1938 so I’ll be facing a huge unknown there as well so all in all I think the “F” factor is way to high with no upside that I can see.

Ideally the main goal of using the BRRRR strategy is to be able to use the same bucket of money over and over again to acquire endless number of properties.  

@Greg KendallThe Capital Gain will be your selling price minus your basis.Your basis = purchase price PLUS capitalized costs (which would include many of the costs incurred to get the property to "in-service" condition...loan origination costs, closings costs) MINUS depreciation taken.And you are correct- the amount you owe is not factored in, although certain loan costs and interest can be either capitalized or expensed.Also @Andrew Reyes brings up a great point- if you intended to sell this property after you had rehabbed and placed a tenant, you may be seen as a flipper and the gain could be taxed as ordinary income.Andrew also mentioned that holding for 2-years will help.

Ideally, I am hoping to find someone with experience with HUD and/or Fannie Mae properties.

Another key factor to consider is whether any of the market has a good property manager since I invest out of state. 

Not ideal location though on second floor.  

With residential rentals, long term vacancy should not be a factor. 

I know that the equity is the most important factor, but if the ROI is great, and the purpose of the Sub 2 is a long term buy and hold strategy shouldn't that make the formula more flexible, since the equity would build faster with a higher ROI?  

I suspect I know the area, but I regardless having looked at a bunch of duplexes in Dallas, I cant imagine that you can cash flow with $4,100 in rents and a $659K purchase price, especially when you factor in property taxes, management, capex etc. the Dallas Property taxes are very high since there isn't any state income tax.