They applied, were background/credit/criminal checked, and passed my requirements.

Anyone here on Bigger Pockets, or elsewhere, telling you it's not, is either an idiot or a criminal.

Things that tell a criminal the house is vacant are for rent signs,  no curtains or no mini blinds in the windows, utilities shut off, yard not mowed,  and you get the point. 

@Jacky Johnson I'd ask to see design of fence.

Do you agree to a criminal and/or credit check? 

Could the Decline recommendation be based on criminal or eviction history? 

Was he screened prior to move in for criminal history?

But I don't know if any of those screening companies actually check with previous landlords either - I suspect they only pull credit and criminal and verify employment.The best approach, depending on your # of units and time available, might be a hybrid - do the quick and easy checks yourself, and then only if someone passes those, turn it over to a screening company to complete the rest.For example, in my state it's free to do a criminal check - one of the few things my state gets right btw :) So I'm usually checking that within a half hour of getting the application.

Further, that there were entire courses and clubs dedicated to teaching these criminals how to con you out of your house, your money, and your first born child and run away before you knew what hit you.

The credit check is pretty generic but does give you a score and it has found criminal and eviction records for me in the past.