A huge worry I have is now that he has a huge personal mortgage how would that even factor into the DTI? 

What is my next step (what contracts etc do I need) without involving realtors so I don't have to pay extra fees to this and that person?

As far as your tax questions, I would personally refer you back to your tax advisor or refer you one if you need it.

I personally am in industrial, but Chicago is a 1.2 billion SF industrial market.

After filing with the court, the tenant sent me a partial payment via CashApp.

This is a 4 day in person mastermind that digs deep into the different aspects of multifamily investing.

You can try filing noise complaints or even a nuisance lawsuit, but whether that will help depends a lot on whether the next door property is inhabited by the owner (less chance of chance, more chance of poor attitude) or a renter.  

However there is filed evidence that the CMX-1 property in question was approved for two residential units and a commercial. 

I've also filed my personal 2023 tax returns and have those available with the STR income included.

I'm interested in connecting with other investors and investor-friendly real estate agents, focusing in MTRs in Kansas City.I'm interested in a 2-bedroom house (SFR or duplex), ideally near hospitals and/or universities and research centers.Are there any real estate agents you would recommend from personal experience?