And, know this: what you don't know will hurt you. 

There's a lot of things im unsure of and any small mistake will hurt since things are tight

Learn...what you don't know WILL hurt you. 

@Landon Sheveland, I don't see how that would help you and it could hurt you. 1.

Clearing potential building sites.  

I am sure no pics is hurting you at this point, some will not even look at units without pics.

According to NYC, STR is hurting housing affordability just like normal people can buy a house or condo near the Time Square and Madison Garden. 

I could put a down payment for a conventional (20-25%) 550k duplex, but I feel it could hurt my chances of buying as many duplexes in a 5 year period (for example) if I go conventional VS an FHA at 3.5%. 

Wouldn't hurt to consult a tax pro just to make sure there isn't a more tax effective strategy but I don't think lending provides any tax shelter.

>on top of dealing with insane lawyers and social workers who believe that less fortunate people can hurt wealthier people.