2-4 paid off properties in great areas with minimal headache is likely life changing for most people who don't overspend monthly. 

It's one of those things that you just have to keep on keepin on because at the end of the day, it only takes one seller to change your life.

At the end of the day, that is life however to Stuart's point, you may want to consider investing in better areas where this does not occur normally if this is an unsettling occurance for you. 

The former provides a much lower return on equity but is simpler and easy to achieve over the long run.The latter is much more time consuming and risky, but provides high returns and a lot of tax advantages. 

Ask anyone with investment property and they'll tell you it's not passive.I earn enough from investments that I could be financially free for life, assuming nothing major happens.

Here are a few I recommend: "Rich Dad, Poor Dad" by Roberto Kiyosaki; "Set for Life" by Scott Trench; "The Unofficial Guide to Real Estate Investing" by Spencer; "The BiggerPockets Ultimate Beginners Guide" found here on BP; "The Book on Rental Property Investing" by Brandon Tuner.

It creates a lot of friction with other tenants and normally creates a poor work life balance for the manager.

A set of new machines can easily run you 300-400k if these are all end of life.

What real-life clients of theirs did you talk to? 

Getting started a little later in life than some, but that's ok.