Currently working with an out of state investor looking to do the same thing but invest in a nice STR out here. 

I am new in BP, and I am looking to understand where I start with learning about REI.I currently live in New York which it's not a good place to start investing.i know the difference between STR,MTR,LTR....

If you insist on going it alone, my advice is to hire a real estate attorney to draft a lease with all the current legislation. 

We have purchased a property for flip that's currently under renovation.

Send it to every address they give you including the current rental assuming it will be forwarded to the address they gave the post office.

I’ve househacked a handful of properties and am currently doing so now.

And as long as they're current and not breaking rules in the lease, they can say rude things to me.But blasting loud music etc sounds past that.

(May also cut significantly into the current cash flow on it)I know you mentioned not doing a HELOC on my primary, but wouldn't it be advantageous to have the ability to pay off the line of credit instead of be stuck in a payment that is much higher? 

I would send them notice today that explains what will happen after the current one-year term ends.

Even if you are a US Citizen and live abroad you may run into issues as you are not currently living/working in the US.