The only way that would work in my view is if you had a plot in prime location & felt you had a competitive advantage in a niche (A+ luxury, student housing in dinky town, etc), otherwise the price and difficulty of building would far outweigh your profit.

This a an 1880 mansion 5500sqft turned into what can be used as a 4,5,or 6 unit property.

On the upside, interest rates are ultra low... so I have to admit I am tempted to refinance this house now from 4% to whatever the market rate is in March 2020.

Every ultra-high-net-worth person I have met did not start doing something with growing an empire in mind. 

That would be sky high for the area, even if pretty high square footage in a great area.What you need to be looking at is a 4 to 6 bedroom in a middlin' (AKA so-so, but not horrible) to nice neighborhood, not a literal borderline mansion in the fanciest sub area of the nicest neighborhood in town.

Professionally done, luxury apartment complexes around my area.

Leaning towards luxury vinyl but between the new waterproof or resistant laminate aswell.

Some "cons" of the 203k are:MI (mortgage insurance) for the life of the loanUpfront MIP (mortgage insurance premium) can reduce the effect of the 3.5% down paymentCan take 15-30 days extra to closeNot all industry partners (Lender, Realtor, 203k Consultant, and Contractor) are as knowledgeable/experience as neededSlightly higher interest rate compared to FHA 203(b), which is the normal FHA loanCannot repair/add luxury itemsSome areas can have lower max loan limits that what is needed to do a 203kExcept for qualified non profit groups, required to be owner occupied for min 1 year  There are many pros to the 203k, but above are just some of the "cons." 

Multifamily is generally a great investment in the DC area....but its among the most competitive niches in our ultra competitive market. less than one 10th of 1% of the metro areas properties are 2-4 units.House hacking a single unit can be a great strategy.

Ultimately I see also owning some short term vacation rentals in key locations in addition to the relatively more stable long term small and large multi family rentals, perhaps some well positioned luxury apartments.I have a decent position now with an excellent 6fig income from my job, and I love what I do...but I don't want to do it forever :-)