I already know that I’m a buy and hold investor and looking to supplement my retirement income as part of my investment portfolio. 

Assuming you're burning gas, one thing you could easily do to supplement the heat in the basement is run hot water baseboard from the domestic HW heater.

Also, many clients are going to a 1-man office staff that is supplemented with a kiosk.

I always tell people-If you want $20k/year to supplement retirement or if you want $1b/year your goals are your goals.

I actually have an email communications automation I built out to supplement Evolve's which I hope to have the document finished next week, I will share that with you if you want to see if you might find it useful for your property as well?   

I know AirGMS, Guesty, etc. does this (even for free for small accounts), however if you are like me and use a 3rd party booking provider like Evolve, you do not have access to your listings for those tools to use so this is a nice supplement for better guest experience if you are in that situation.

I wasn't trying to get into real estate investment for any other purpose than supplementing and paying off the mortgage. 

For me, this is my retirement plan, or at least supplemental retirement plan.To the argument that my job can end tomorrow, all I can say is that I've been a freelance all of my career of 27 years.

I would like to learn more and eventually supplement my architecture income with a BRRR income stream, but I am looking to learn and find opportunities to invest.

The solution to that is getting a second job to help supplement the income.