It caused our fearless leaders to enact laws designed to prevent all of that from happening again, most of which won't and a lot of which hurts more than it helps (like the FHA 90 day anti-flip rule--seriously?!).  

If you're planning to do any flipping/rehabbing, those things are what will break you... preventing them (or budgeting accordingly) is big.

Do you only fix things when they are broken, or are you vigilant about providing preventive maintenance.

I was wondering if there is a difference between "assuming a loan" versus taking over a loan in a subject to.If I do a subject to deal where I take over the loan of the current owner and they transfer the deed over to my name, how can I prevent the triggering of the "due-on-sale" clause?

A lease doesn't prevent anything you've described... it simply gives you recourse against the tenant in the form of an eviction if they do those things. 

Now I have checked the plumbing and  found no issues and I normally am pretty diligent about repairs and preventative maintenance on my rentals but I don't want to open a pandoras box here.  

I think most of us (who pay taxes) care about general injustice, and don't mind to see the government step in and set up shop to prevent these things from occurring. 

This isn't my favorite income idea but there is no doubt collecting fees is a way to prevent more costly mistakes.

This is simply to prevent giving out financial data to all of the window shoppers.

Make sure outside spigots work, or people will run hoses out the windows and leak water all over your floors (get over any idea that you can prevent them from using water outside by removing spigots; people are going to do what they need to do).