One concern that I have is that I need to be able to sustain this during a downturn.

I haven't left more than 5-15K in ANY on my properties and have created a lot of equity in all of them except Toledo.

For an investor that is looking to create wealth and keep doing what they are doing this is a great strategy.  

Others have simply created a new listing and had the seller notify guests about the change.

While I use it primarily for noise concerns (it alerts me for sustained +80 decibels), it's also handy for cigarette smoke and tracking temperatures (in addition to our Ecobee thermostat)- sensors on all exterior doors and possibly windows (which you might have via smart locks for the doors)- exterior camsA recent guest for reasons only known to them set the thermostat to cool and 60F in the winter (where it's currently a balmy 11F). 

Once you're ready, create a goal (e.g., "I will buy at least one single-family home, duplex, triplex, or fourplex before the end of 2019") and then do it.

I use this and share with my team (i.e) drone photographers, VAs, reatlors, partners, etc.Zoho Forms, I use this to collect info from leads, buyers, etc.Zoho Desk, this is a ticketing where all inquires go to and since it integrates with Zoho Forms, it creates a ticket within Zoho Desk + New Lead within Zoho.Zoho Cliq, similar to slack, I communicate with my team with this software.

@Joseph Beilke, @Michael Baum, @Mike Lambert, and @Ian Fortney, First off, I'd like to say that investing in the United States in general creates a better return than in Costa Rica.  

After reading Brandon and Brian's book, The Multifamily Millionaire, Volume II: Create Generational Wealth by Investing in Large Multifamily Real Estate, I'm a bit puzzled as to if the GP's must have real estate experience, or if someone can connect enough professionals/companies on their team to execute successful investments.

Helps you stand apart from similar 4 bedroom homes and if you choose to pursue a rent by the room strategy in can create additional cash flow.