I can't imagine one of them bringing in 100K. 

I can imagine that, with the wrong mindset, it could feel like an invasion or disrespect of your personal space. 

As someone who has only done out of state investing because the Seattle market didn't work with my goals I would say it is totally achievable and likely in less time than you are imagining.

Imagine these older folk's financial planners did not plan on high inflation. 

Look at buying my first investment property (probably a house in the 100-150k range) and begin looking for a tennant.I can imagine there a lot of different theories/ideas with what one could do here--I am just curious to see what other people think.

Can you imagine a tenant knowing they are moving out in 6 months.

I'd imagine that it is quite location specific as well, so I'd suggest poking around a bit on HipCamp as if you were a camper, and see what's around you. 

I have several questions - imagine being able to split up property ownership into tiny pieces or having every transaction out there for everyone to see, all secure and tamper-proof.

Imagine having getting 150,000 points intro bonus for spending 6k in 6 months for Amex or Chase for example.

I'd let my imagination run wild.