WArning:  You are asking legal questions in a forum online. 

I constantly hear people online (Social media) talking about getting an FHA loan and house hacking a 1-4 Unit property.

A very few online.#2. 

It's important to know and consider the max rent potential, cost of rehab, and municipal requirements (rent control, registrations, inspections).

Check out other online guides available here: https://www.biggerpockets.com/guides3.

You may be able to go through online court cases to see what names popup over and over again.

I have not been able to find really anything about them online.

City referred to me some rule called Green Code rule from PGE but cannot find any info on it online.

I could also leave a unit within the multifamily property vacant when I am abroad to use for storage if needed, to better help solidify the "primary residence" requirement.This is a pretty specific question, so I haven't been able to find any previous posts on it or any helpful literature online.

I asked my realtor for a PM referral and I talked the PM and he said it sounds like a decent deal and I researched inspectors online and the inspector went and checked it out and he said it had good bones and he said he'd buy it as a rental property.