@Robin Carriger From what I've seen (read), which is certainly incomplete, the ibuyers concentrate on specific cities or metro regions.

Stocks because less time, more liquid, not a ton of concentration if you do it right.

Of the 11k jobs, are those primarily concentrated in one city or dispersed around the organization worldwide?  

I am not actively selling anything currently as I am concentrating primarily on actively investing in real estate.I do sometimes take on a protege/apprentice at my discretion. (1 this year)  The majority of the money I make from them is from JV deals with them. 

Phoenix has generally expanded concentrically so investing in the out rings has historically worked out well.

With little competition from regular buyers, investors dominated the market for a few years, setting a floor for falling prices around the Sunbelt cities where they have been concentrated.

SFHs are not necessarily better suited to ride out a downturn than MFH - it depends - but they have more exit strategies and don't concentrate all of your exposure into one geographic location (unless you own all the houses on the block).

I want to concentrate on the high return items and the items that provide me the most joy, but there are always things that need to be done. 

I usually concentrate my efforts in one area to avoid the need to establish teams all over, allowing me to consistently support and foster my existing team.

However, reliable tenants are the exception, not the norm.At least one tenant segment will have a high concentration of reliable people.