No Agent will guard your interest like you will for yourself.

Especially when you hear his seller calls and how he takes their guard down.

All my money is under my control and I am guarding it with my life.  

The Pros are: they rent quicker(at least in my market), offer amenities like fitness centers, pools, security guards, secure parking etc, low maintenance since you own from drywall in, you don't have to pay to cut grass, paint the exterior, replace the roof, cheaper insurance, not as many tenants to do too much damage to your property. 

They catch me off guard and I lose my place.

I would suggest trying to work out an extension, although the bank may request more money upfront in exchange for a financing extension, at least this gives you more time to tap a another non-QM lender.I also agree if you had a financing contingency in the PAS agreement, you should try to make this claim if all else fails and definitely be strategizing with your attorney.This pandemic has caught everyone off guard, unfortunately it's just bad timing.

Remember analyzing the deals, putting in contingent offers and doing our due diligence on the properties every step of the way are the safe guards that keeps us from not having to rely on our emotions or nerves on these deals in the first place.

But would the typical landlord's insurance policy guard against this?

Roofing is statistically more dangerous/deadly than being a police officer, body guard, security guard in a dangerous neighborhood, and just about every profession. 

It is generally wise to let the tenants know beforehand (before they submit the application, I mean) of your qualifying criteria so they are not caught off guard if they know of something on their report.If you deny an applicant based upon what you see in their credit report, be advised that you are required by law to tell them that you denied them based on something you found in their credit report, and you are required by law to provide them with information regarding how to obtain the report.