Ie deteriorating roads, failing retaining walls, bad roofs. 

They wear and deteriorate quicker.

It's deteriorating with no one living in it.

If you keep them month to month, you can move them on out if that deteriorates.  

Land and some land improvements are one.There are improvements to land that are depreciable, walkways, retaining walls, shrubbery, driveway, fencing, etc these all have a useful life and will deteriorate over time.Tax accounting and financial accounting do diverge when it comes to depreciation.

This begs the question, is the average BP investor jumping into a SFH investment because that is what is available to them based on capital, and if so, that's totally fine IMO... or is there a population of investors that fundamentally prefer buying SFH in deteriorating economic markets for short term cash flow over the longer term, risk adjusted growth of a successful syndication? 

Agree with @Jay Hinrichs     It will take time to unravel deteriorating mortgages.  

There are acres of dumpy, deteriorating warehouses along the duwamish river that seems to me could be rebuilt as a whole new urban waterfront neighborhood.The city (and surrounding ones) do need to make it less complex and easier to build at all scales.   

Continued water intrusion can result in deterioration andfailure of the foundation.Foundation - CrawlSpace53 Due to the water leaking into the cellar at joist height many of thejoists and some of the sub floor has moisture damage and rot.Structural repairs will be needed and joists will need to be replaced.Any time you have moisture damage and rot mold is also a concern.Recommend testing for mold prior to work being done.View report*This link comes directly from our calculators, based on information input by the member who posted.

This type of legislation is the beginning of a deterioration of housing quality, and will ultimately lead to less property tax revenue for the taxing municipalities and schools as property values are decreased.