How would I approach the investor or how would I make sure they don't go behind my back and kick me out of the deal?

I already knew what he was saying as I follow lots of economists but there was something about his presentation that confirmed the path I am an on and I felt like he gave me permission to fully unlock an aggressive approach to acquiring property. 

Interesting approach!

It’s super easy to feel overwhelmed when you’re trying to teach yourself something and there’s a million different ways to approach it.

Any information on how I can approach this here in Chicago, would be extremely helpful.

There are a couple of ways you can get started in RE; the most common approach is house-hacking.

I think your househacking approach will be a great strategy in most areas.

Especially depending on your approach and if you're ok with appreciation and not cash flow (older houses will have maintenance and newer houses have hefty HOAs and MUDs). 

Those are the three ways that I know that you can approach the decision.

And from what i've gathered through reading the text messages and emails the tenant had sent to my parents, the tenant really did just install the AC without notifying us. and true, I don't know the extent of their business relationship, but it looks very professional and healthy to me.