You would required insurance binder on thier dog,  proper verification of immunization. and dog must be leashed if outside and in owner control at all time.But as soon as thier lease is up the dog must leave or they all can leave.

I do understand that land trusts don't make you immune to the due on sale clause, but am I correct in thinking that they greatly reduce the chance that the lender will notice? 

I filed a claim with the city and the insurance company contracted by the city responded that "A public entity is immune from the liability in the absence of having been place on Prior notice of an issue.

So, as a borrower, you are, in a sense, immune from prosecution.PML’s are unfamiliar with loan servicing and foreclosure regulations, thus allowing borrower months or years before realizing and consequences.I’m sure there are other advantages to the REI but that’s all I can think of right now.

And new construction is not immune from major cost items.  

Granted, I'm not saying I'm immune to those problems, but I can offer this; if I faced these problems or recognized the potential for an area to "downgrade" as you wrote then I'd 1031 Exchange myself out that door and pivot into a better neighborhood or market or asset class. 

No one is immune from unforeseen events. 

Say, I do not want to get the preforeclosure leads (pretty houses with no equity) - any way to be immune from those useless leads when advertising outdoors?

The major cities in Cali are not immune to downturns but the general trend has been up for many decades. 

My impression as well would be that free-and-clear properties make trial lawyers' mouths water, and that the presence of the debt will give some natural lawsuit immunity should you become a potential target, so that has some value in our litigious society.I would also take advantage of the low fixed rates and great buyers market, using your payoff cash to grow your little empire.