Even as someone who owns multiple rentals I still heavily rely on tax strategist and CPAs. 

I never even considered a leased STR.

I use pricelabs on all my listings and have really enjoyed it. 

They liked my offer and the rapport I built with them and decided they wanted to sell to me even though another offer was higher.

Had mortgage and note on the property.Buyer failed to get insurance is my understanding even though it was in the agreement. 

One might even invite you to visit one of their projects to talk about it in detail and give you a peek behind the scenes. 

If so, you may be able to wholesale the property to someone (perhaps even someone in one of those $400,000 houses) in such a way that you and your grandmother come out whole.

You've gotten some good advice above but $100 even seems cheap after looking through these photos. 

Putting less down may subsequently put you in a break-even scenario or possibly even a negative cash flow.

Do another heloc if anything, sell your primary, OR find creative ways to cashflow even more from this property so that way you can subsidize your interest payments for your primary home.