What might help you for the next attempt is to read (BP's book written by yours truly--The Hands Off Investor), and network (join a community where investors discuss deals, trade advice and observations--coming soon will be Passive Pockets, an offshoot of BiggerPockets which recently acquired the popular passive investing group Left Field Investors).

The only way to effectively determine this is by driving neighborhoods, walking properties &  observing the daily routines of those who live there. 

I'm do for a assistant. 40 yrs to observe and construct in this industry.

This is when most guests will observe any issues, and it can be nipped in the bud right away.

Again, nothing I say is legal advice, just merely observations of past clients doing things similar. 

I found an auction property, drove by it and sent him a long email with my observations and values that I came up with.

I've joined here just mostly as an observer.

What I have observed, the highest is seldom reached.

Any other clues or observations to make to understand if the tenant is good?

I will add to the above information that this is the practice I have observed when dealing with short sales.