If I could use that money to purchase more real estate and then finance the car I would probably take that option. 

Have you tried reaching out to any local mortgage brokers in the area for more options?

BiggerPockets has options to search through investor-friendly resources that you are looking for here too. https://www.biggerpockets.com/real-estate-companiesGood luck on your STR journey and let us know any updates or questions that come up!

Perhaps they offer a favorable refinance option if the property has appreciated to the point where the current loan amount satisfies their non physician loan LTV underwriting.

Another option would be to consider Starlink. 

There's just so many options out there but the first step is getting that first deal. 

You have 2 solid options!

Credit unions can also be a good option.

So I’m trying to see if I take that equity off the table and re-invest the sale proceeds in another market across more doors where we’ll see better appreciation, OR if we continue keeping it as a rental and work on principal pay down even though the rental price has been coming down and the home is not the easiest to fill because of the above average price for the C- to B neighborhood.Ultimately, my stated goal has been to build appreciation (over cash flow) by acquiring 1-4 doors per year for the next 10 years to allow my wife to retire (or be work optional) by the time she's 50.

If you can get someone to do this I agree this is a great option.