The ownership changes, and no real wealth is built. Those people are merely surviving, just like their employees and their customers.
Why?
The owners move on when they find something more lucrative or they've stacked enough capital to move on to bigger and better endeavors.
The fact that you never see a corner store closed indefinitely is somewhat indicative of it being a money maker
Easy..
100k > 20k all day everyday.
It would be extremely difficult to find a place to stay and a reliable car off of 20k
But with 100k, I can easily find 2 spots that I could pay for where my 10 dependents could stay, and that's real. Plus, I'll have enough bread to have 2 dependable rides. If food is bought in bulk, you could feed 5 people off of 500 dollars a month easily so lets just say 950 a month for 10 people or more. Mexicans that open up tire shops\garages\restaurants\etc do it all the time until their relatives can stand on their own.....
There is no way you could pull this off with a 9 to 5 unless you were making 140 k before taxes, and how many people outside of the coli making that kind of bread....??