Cheaper, faster, and just as effective, if not more so, than the old-fashioned certified mail, which was the only way to get proof of delivery before there were scanners or the Internet, and they can't avoid delivery by refusing to sign.If you have access to their telephone numbers and/or email, you can also send notification that way.  

If they call, reply in 24 hrs or less, fix their work orders in a timely fashion.  

I dunno.I had to deal with this stuff during the 2008 crash, and what happened back then was tenants just moved in with relatives and gave me proper notice or we worked out something in an amicable fashion - which never included them getting to stay rent-free or without owing any rent.

A Biography of George HW Bush -The Perfectionists: How Precision Engineers Created the Modern World-Spark: How Old-Fashioned Values Drive a Twenty-First-Century Corporation: Lessons from Lincoln Electric's Unique Guaranteed Employment Program-Good Profit: How Creating Value for Others Built One of the World's Most Successful Companies-The Great Mental Models, Volume 2: Physics, Chemistry and Biology-The Outsiders: Eight Unconventional CEOs and Their Radically Rational Blueprint for Success-Conspiracy: Peter Thiel, Hulk Hogan, Gawker, and the Anatomy of IntrigueWhat books have you read so far?

It appears they do not want you to enter because they are violating the terms of their lease in some fashion.

In that case, you'd be double-dipping and no court thinks that's right.So, rule of thumb, don't charge your tenant for problems that have happened while using things in a normal fashion. 

Forget what all these naysayers think, your body is your temple, and you have a moral obligation to yourself to make your millions the old fashioned way, in court.

Then, they'd usually want a request via fax on letterhead, which I did not have, as a resident manager working for an old fashioned owner.Other than using other good sleuthing techniques and credit, criminal, eviction, employment checks - your next best defense is a month to month agreement.And remember that you can deny them for nearly anything you can think of.  

I have this old fashioned idea, about keeping personal and business private...Some third party services will list to Facebook Marketplace, but my guess is then your giving up the Facebook chat.

We are closing on our second SFH investment in 1 month, so just also taking notes for things that I might not have thought to spell out in the lease - such as taking down holiday decorations in a timely fashion.