I've been through situations like this.Hopefully the family pays rent and this becomes a non-issue.If they don't pay the rent, you need to be understanding and kind, but firm.  

Now a-lot of times you buy a home from someone with seller financing and they hold the note for 6 months to season it and then sell the note to another investor or a firm and then it will most likely show up on your credit because these are more sophisticated investors.In regards to the benefits of owner financing you won't have to pay closing costs to a bank.

I've never been so disrespected and found such an unprofessional firm, and I have property mgmt companies in 4 different states

They were a law firm who hunts class action suits to go against companies. 

I've done some preliminary due diligence (as the lender) and feel I have a pretty firm understanding of how it works.

There is risk in both options & as an investor you need to weigh those risks & stand firm on whatever you decide. 

Got a statement every month from a very reputable, conservative firm.

The combination of its growing tech & healthcare sector, long-term resilience to climate change, and relative affordability makes it an interesting place to start our real estate journey.I spent a big part of my career in hospitality real estate consulting at a Big 4 firm, but I left to explore new opportunities and decided it was finally time to take the leap into real estate investing.

Are there any creative things that could be done to get to my goals or from your standpoint,  or is it pretty well a firm "not gonna fly" type scenario? 

You need a firm estimate for the remainder of the work as your funds are limited (like most people who don't have an endless amount of money).