House hacking means having rental income to pay expenses and reduce one's cost of living.

Be advised, a number of banks have closed or severely reduced their HELOC programs.  

Appraisal (if the appraisal that your lender engages (the only one the lender will base your mortgage on) comes in less than the offer price, the seller can reduce his price to the appraised value and all continues on - or you can walk with the return of your escrow; if the seller won't budge and you still want to buy it, you would have to pay the difference between the offer price and appraisal at closing).3. 

If you do a good job you can either do more or bigger deal flow or reduce your cost of capital for a fixed size of deal flow. 

If I can reduce my monthly payments by $200/month, would it make sense to refinance?

I plan on reducing rent 20% or more if there is a surge in vacancies when things go south. 

I think it is a great way to reduce one of your largest monthly expenses, rent if not live rent free.You may be eligible for tax deductions that you were not entitled to before. 

This will reduce costs to minor park maintenance and taxes.

There are discount brokerages out there you can work with that offer reduced commissions but you get what you pay for as they say; working with these brokerages will limit the number of properties you get access to because the traditional brokerages don’t like working with them.

Overall costs need to be reduced by $8k for me to do it.