Next if it will only harm your property if it falls then its probably all on you.You will absolutely need either a temporary or a permanent easement to work on your neighbors property.

They went out same day and installed a temporary fix, and had the new unit installed  and the warranty registered early the next week, all at $1000 less than my property manager had quoted.  

I've considered buying an in-between 200k home that I could house-hack as either a temporary home (in case we need to move etc.) or use as a rental.

Because of the high equity value, I don't want to co-mingle this property with others, as well as having new temporary Members coming and going.

Have a clause in the lease which states if the tenant does not leave when the lease expires, they are responsible for all expenses incurred along with providing new residents with temporary housing, etc.

Renters insurance will cover their personal property, and many policies will pay for temporary housing for a limited time.If the home becomes uninhabitable the tenant has the right to terminate the lease without penalty upon written notice to you.

Your forbearance to mod agreement would outline the payment schedule for a temporary period i.e. 3, 6, 12 mos for a trial period with the existing loan terms in place before it is permanently modified.  

Sheet vinyl is a good temporary and cheap option for rentals. 

Well it certainly sounds like RTC is only temporary fix.

If you are using her money as a temporary bridge then maybe you pay her extra or you reduce the risk she is exposed to.