When you say your house hack phase has passed, are you saying you DON'T plan to occupy a unit of the 4-plex?

The tenant who occupies the property pays the rent.

For example in many jurisdictions I can STR units in a duplex but cannot STR an ADU (some jurisdictions will let you STR if you owner occupy).

Quote from @Na Wilson: I have a source (depending on credit score) that can do a 90% LTV DSCR loan on non-owner occupied real estate. 

- what if someone is occupying the living areas more than someone else and it causes an issue? 

It's not like a REO auction or tenant occupied property. 

Do you want to occupy it a couple weeks a year? 

A colleague of mine has bought two properties owner-occupied back to back in Arlington (with a 5% rate and a 7% rate) doing basement conversions and renting rooms, lowering his effective monthly payment on each property to sub 2K each time.

I owner occupy the home, renting a room to a friend at $650/mo, and the lower unit rents for $1850/mo - total rental income of $2500/mo.

If you don't plan on paying cash and have to leverage with an owner-occupied loan product then you should set up your LLC as a property management company because you will not be able to borrow in the name of the LLC.