Multifamily real estate has traditionally been a stable asset class, and the Washington D.C. metro has traditionally been a stable market area, making the two together a good safe bet, especially for anyone with a long-term view of their investing strategy.

I started out with a house hack, and I would say that that was definitely safe for me when I was in college as I could afford the Mortgage even if my renter didn't pay.

Goal would be to acquire 20 rentals by the age of retirement, with some already starting to be paid off.I am in the same boat as you, and I focus on safe appreciation all day (small cash flow for safety and then focused on markets on that appreciate). 

You may be safe to get non-commercial F/F adding up to 2 ADUs to a duplex even though by rule this does not qualify (in my area I have never heard of this being an issue). 

The property tax savings are going to be in the ball park of 40-60%, but to be safe you should double your expected repairs budget when calculating the NOI.If you have any other questions, or want a more in-depth response, I would love to help!

My primary goal for investing in real estate to grow my wealth and generate a bit extra income- not replace my day job.As the first investment, I want a safe investment with a goal recycle my down payment for a second property within 12 months and focus on learning & long-term cashflow/appreciation.

Then you can safely complete the 1031 exchange. 

I'd also be careful when using a heloc for the down payment and getting a loan on top of it due to the zero equity situation -Be safe!!

I'm assuming that this situation wouldn't pass inspection, but one could argue that all the spaces the guests have access to (i.e. bedroom, bathroom) are safe and habitable + the guests wouldn't be exposed to the kitchen.Also, do the city inspectors inspect other parts of the home the guests won't access (i.e. inspectors check the basement for water infiltration even though no guests would ever be living or even going down there). 

Your diligence can make all the difference in ensuring safe and successful investments.