Detailed Improvement List (arguably the most important.

That is in arguably the worst of the Phoenix, AZ weather with temps in the mid 110+.

Thanks for the book recommendation Jonathan...Create a personal circle/sphere of influence list with all of your friends, family, neighbors, former coworkers, etc. and contact them regularly.Perhaps the best (and arguably most difficult) source of new business comes from calling "For Sale By Owner" listings on Zillow.

Short term renting like Airbnb is more time intensive than Long term rentals.If you hire a good PM though it certainly takes some of the effort out of it.Syndications are arguably the most passive way to real estate.

For me it's happened arguably twice in the last 20 years.

At the end of the day, no one is getting rich off it, but it helps at least some dollars not lose too much to inflation (and arguably potentially slightly beating inflation). 

The area is arguably the most important aspect of any deal.

Knowledge is arguably more important.

That is arguably a little more risky, but it works for some people. 

A mix of many assets in conservative quantities arguably is the safest way forward.