However, I'd be surprised if you weren't able to make house hacking a duplex work numbers-wise in medium-sized markets and larger, especially if you are willing to set up the vacant side as an STR in a travel market with reasonable STR regulations.

Since short-term rentals in the US could become over regulated or downright illegal (where they aren't already), the resulting cash flow and profitability could drop hugely if not becoming downright negative in case of a conversation to long-term rental.

Strictly speaking from a tax perspective, you cannot take more than 3000 in losses even if you harness more than 50k in losses (Unless, if you have other capital gains). 

It seems insane to me, as my monthly recurring expenses are $375 before food, & $110 of that is Public Storage, so it's $265 once I move in.How strict is this 3x rule (OF THUMB)?

This requires strict discipline.

Trust me this is not worth getting into a legal battle over trying to make an exception, this is a business that is heavily regulated and guarded to protect all tenants rights.

Other states treat upfront rent the same as a security deposit, subject to the same rules, regulations and interest payments.

You have to be strict and tell them that the rent is due 5 days before the first of the month.

In this situation, could we set up a Land Contract such that my down payment would be used strictly to pay off the property taxes, and my monthly payments to the seller would essentially be equivalent to what I would charge a tenant to rent? 

I've been told to the best of their investigation, the title is clean.In NY, as I understand it, the state regulates title insurance.