As far as benefit to the seller goes, @Matthew Paul I think you are probably right on the money and regardless of whether they would have preferred to stay in this house rather than move, it is likely providing them some excellent cash flow; and I'd be hard-pressed to come up with a deal that serves both parties better than the current situation. 

What are the benefits of SUB 2 financing a property?

Depending on how you use the property, you may benefit from a cost segregation study and bonus depreciation once the property is in service. 

Generally there are multiple units for each "zone" if you will when I've seen them installed.Regarding your problem at hand, I personally would simply adjust your plan to move and make your initial plan to get the current issues resolved, while costly now, in the long run holding onto the unit will likely pay off. 

A benefit of this setup is that VRBO still processes payments and handles the transaction.

It is quite the adjustment, but I LOVE IT HERE. 

It’s worth considering self managing as a STR for depreciation benefits if the demand is there 

If you have material participation, you can benefit.

Explore multifamily or out-of-state investments for higher yields.Setting up an LLC provides liability protection but has no tax benefit for you now.This post does not create a CPA-Client relationship.

Then adjust based on both your and their view of the world.