And the owner is very responsive to questions or issues (emailed him at night and received a reply within a few hours).  

I got from this LP the name of the owner of 711Rescue: Zak Shaik.

It seems they were non-paying tenants even under the previous owner, who likely sold the property because of them.

The old owner unfortunately locked his tenants into $800 leases which scared away some buyers before he listed.

While I have a fantastic rate, the co-owner's giving me the option to refinance or he'll force a sale.

For example, maybe you will get to 10, 20, 30 houses and then find an owner who has a large portfolio and all of a sudden you are at a high door count and now need to hire, need to build your policy binder, and all the other stuff that comes with running a business.

I'm an investor, flipper, and property management company owner in central CT. 

You may also be able to start sending letters to duplex owners explaining who you are and that you want to own and live in a duplex, etc.  

The owner, a family member of one of our buyers, inherited the property through probate, but they weren’t equipped to handle the renovation.The house had been left in disrepair for quite some time, with the previous owner struggling with mental health issues.

Since you'll be owner-occupying, take advantage of low down payment loans like FHA (3.5%), Conventional (5%), VA (0%), or a 203k loan for renovations.