@BargainValueHunter, great, great, great question! I've been thinking the same thing, when Buffett and Ackman said it's hard to scale, what do they really mean?
@ERICOPOLY, I've talked to a few individual home investors, they all said property management companies don't do much. They ended up doing most of the work themselves. Now this does not mean all property management companies are like that.
Also, I'm curious, when you go buy the house in Las Vegas, do you actually go check out the house? Buying 100 houses in a few months seem like labor intensive, but I could be wrong.. :)