+1 Dhandho Investor describes this same story and the philosophy / technique to replicate this approach in your own life

https://www.amazon.com/Dhandho-Investor-Low-Risk-Method-Retu...

I don't know about Chinese or Korean communities but a lot of the indians that you mention primarily come through via family ties.

One person gets here (alone or family) and files for immigration papers for their immediate relatives, starts working here (usually at an establishment of a relative or a person from the same community), makes enough money, transitions to setting up a new business and the someone else takes their place at the previous establishment. That's how the motels and 7/11,Dunkin etc. chains are run ..

This book had a nice description of this phenomenon. http://www.amazon.com/Dhandho-Investor-Value-Method-Returns/...