I have to have safe options since a failure would be catastrophic .

I will likely post some information i have first hand knowledge on concerning recovering from catastrophic financial changes later in life. 

But I can tell you that is perfectly safe 99% of the time unless there is a facility malfunction resulting in a catastrophic failure (blowing up).

As far as currency collapse or nuclear war, those are catastrophic events that will not be a buying opportunity.

You should insure the property as of the closing date so any unforeseen catastrophic events are covered.

Assuming you are putting 20-25% down, you could pull a HELOC out or cash out refi in 2-3 years and use that money to replace your AC with that  I don’t know if I’d rely on interest rates going back down into the 3’s unless there’s another catastrophe.

I also have a $175,000 line of credit at the ready if something catastrophic happened.

If you work on anything electrical, structural, or mechanical and at some point your work suffers a catastrophic failure, that could be linked back to you.

What may look catastrophic on paper may in fact be manageable and what may look like a cream puff on paper could in fact be money pit that makes Butte's famous Pit seem shallow. 

Property insurance is not intended for minor issues, it is for more catastrophic major unforeseen events.