Lawsuits are rarely quick nor inexpensive.

Go expensive on equipment and melting products because a slip and fall law suit will cost you thousands and raise your premiums.

Agree with comments of @Wayne Brooks (we had to do a friendly lawsuit to settle title for our $2k/unit multi).  

Have there been any horror stories about renting out in-law-suites that don't have a separate address?

Making yourself an unattractive lawsuit target is the only way to deter lawsuits - you can't actually prevent them.

According to wreg.com, the couple has filed a 1.3 million dollar lawsuit against Arnaiz and is alleging that they have suffered from emotional distress, anxiety and loss of sleep.

Any pending lawsuits?

Besides that, I am guessing that by state law (even if not the case why open yourself up to a lawsuit), you need to change the locks when you have a tenant turnover.

You learn this after the first law suit and documenting everything and being totally honest will not prevent all lawsuits, unfortunately. 

She has not produced any medical bills.She hired an attorney and now there is a law suite, demanding 18K, to make repairs to her condo which now includes the kitchen and laundry rm. floors and doors, which was not affected by the leak.