The removal of the Taxable Value cap and the switch to Non-Homestead millage rates can double, even triple, the property taxes.

They can get time, but they’d all have to double or more their investment (if any of these assumptions are right).  

Which is more profitable: an assignment or a double close, and why?

The note can't exist as a stock simultaneously because in the securities world it's a fraud known as double dipping.

Bedroom requirements can change depending on local code.

Due to increased rates i did not refi so i did not get opportunity to see how an appraiser valued the half bathroom but the comps with same bathroom count had crazy valuation for the additional half bathroom.Taking under utilized space like a work area to add a br where the added br does not put you above the normal for the area can add value.Similar if a neighborhood is virtually all 3 br and 4 br properties and you find a 2 BR, it could be a value add to add the bedroom via new construction.  

From what I’ve read on BP, the city of Alexandria seems to be friendly towards STRsI would then also potentially rent out one of the upstairs bedrooms as a MTR or LTR.

Obviously, two factors are responsible for what will likely be more than doubling our money in 3 years.  1.

New drive up units have almost doubled in price in the last 4 years to around $4,100 erected; not counting land and other costs. 

Finished basement with an added bedroom and enclosed laundry area.