Homeless problems in CA worsen.  

But letting it continue to worsen means the fix will only continue to cost more.The in-between answer is to somehow mark or show the size of the damage and continue to monitor over the next several months. 

It has been structurally sound for at least 10 years since the addition was built, foundation company even mentioned in passing it'll probably be fine structurally for 10 years if I don't mind the sloping floor slowly worsening, but no guarantees on timeline.Is this a terrible idea?

The further you go into this the more there will be at stake and, presumably, the relationship will have worsened.

I have done some research and read news articles published by reputable sources and it appears that several western states are going to be badly impacted by the worsening weather conditions and droughts in the coming decades.

., arguably, it's super-conservative Investors such as yourselves that help to worsen the divide between neighborhood gradings.

With the worsening laws and regulations I'd stay clear from every tenant friendly state and look for landlord friendly state with no state income tax. 

Given global climate change, this trend appears to be worsening.

I would speculate that there is a possibility that short-term rentals will become a much more popular option for homeowners and ultimately will take a large portion of the blame for the worsening of the rental housing supply despite the incentives for traditional rentals being diminished via government intervention.

If the intent is to hold long term, having a buffer may prevent the location from worsening over time if the city as a whole trends downwards.