The Inspector found Deteriorated Piers and Support in the Foundation.

The problem with older properties in general is the insulation in the walls has deteriorated from it's original noise level dampening and the floor structure has weakened with age.

Most financially successful investors in those neighborhoods let the property deteriorate in favor of cash flow.

Well, long story short, owner would lose payments because the condition of the units deteriorated to the point they failed inspections and each time repairs were made and a reinspection took place more repairs were needed, so came to a point the properties were let go... 

Figure if after 30 years you lose 20% output due to deterioration.  

As I later learned my property was on the fringe of the war zone which later was absorbed into it when the housing bubble burst and my investment further deteriorated.

I can attest that recently rents went down 20-25% for roommate setups and the market got flooded with inventory from Airbnb units that got vacant (no more short-term), intl students leaving SF (seems like for the next 2 years and with a deteriorating relationship with China, maybe even longer), ppl moving out of town due to covid ("why pay high $/sqft when you can get a better bang for your buck somewhere else 4) tech companies are allowing remote work.

They lived in another house we owned for a year, but when her condition deteriorated and she needed her parents to move in to help, we offered another house we owned that had a finished basement with two bedrooms, full bath, kitchenette. 4.)

There was a deteriorating detached shed in the back yard of one of my places. 

Owning a passive investment across the country can deteriorate very quickly if you do not have someone that truly cares about it keeping a watchful eye out.