Making decisions based on it alone would be a big mistake, which it sounds like you understand. 

Their landlord wasn't very friendly, and would not occasionally surprise them with a gift of booze and porn mags.What are the mistakes you've seen other people make?

Make sure to let him know how he is protected, and go over worst case scenarios, and let him know how you will mitigate them.

You may have wanted to go to a private college and not work while going to school, but if the degree didn't get you a high paying job, you made a mistake.

Like Robert Kiyosaki said, vacation homes are the number one worst investment.

The biggest mistakes are typically at purchase - over paying or missing large rehab items needed.

The caveat is that an agent with less experience and knowledge of your area will make more mistakes in this area. 

I said 65K ARV to expect the worst since this is my first investment home.

Plan for the worst when dealing with huge projects because there are so many unknowns when you open up walls.

I realize this is likely very location specific, so I'd look at somewhere like Orlando, FL where the market is hyper-competitive as a "worst case" scenario.As background, I am very new to the idea of STR properties as an investment option and am trying to wrap my head around how best to evaluate properties.