My recommendation would be to iron out what you're looking for as an investment goal.

Based on the info in your post, my recommendation would be to turn these assets into well oiled machines and max out their NOI.

You'll learn a lot here.I recommend focusing on 1 strategy/business model and going all in on that one until you've mastered it and it's stable.

Any recommendations on how many rental properties per LLC?

When managing multiple applications, it’s crucial to ensure your process is both fair and compliant with local, state, and federal housing laws, including the Fair Housing Act.A best practice to avoid any perception of bias or confusion is to process and work on one application at a time.

I'm eager to learn more about:Identifying undervalued properties: Are there any specific strategies or resources you recommend for finding deals below market value?

What would you recommend?

I recommend renting it as a 4/4 and being clear about the set up. 

I would recommend you look for a good neighborhood to buy a multi family in.

Since they've lived there so long, I recommend giving them 60 days to move as a means of softening the blow.Third, don't negotiate or accept excuses.