As a property manager, I have been tasked with this before on a few occasions.

I have had 2 occasions where AirBnB did not sync a VRBO listing.

I routinely pay to have the grass cut and on multiple occasions made repairs to the property.

On several occasions, I've had contractors drop their price 5-15% when I told them I was comparing quotes.

The PM could also check the rental on occasion just to see if the tenant has willingly vacated.

It seems like most of the scammers that want a no-fee pet won't even spend the money for the vet and dog license-- they'll just move on to ask an easier landlord target.If you know the rules, you may on occasion need to accommodate an ESA but you'll probably weed out the VAST majority of the scammers.

Even great ones may seem to appear on occasion that you should still take the time to review their work on the first few jobs. 

I wouldn't say it's always a red flag, but it can be on occasions.

I buy and hold SFR with my business partner and on the occasion we sell a deal here and there.

I had two occasions where the tenants looked amazing on paper, and connected with them really well during showing but turned out to be super incompetent tenant and called me about everything inconvenient about the house (i.e. smoke detector out of battery, spots with wall paint, natural porous holes on a travertine floor tile).