What exceptions? Don't you have any restaurants or dry cleaners or any other small businesses around where you live which were started by poor immigrants?
I hope you don't think only a multi billion dollar companies count as success. The point is: a lot of poor people start businesses all the time and a lot of them end up successful.
I would not count working 12+ hours per day 7 days a week, while barely making each months rent as success. As far as I can tell that's the reality for most non-franchise stores, small restaurants, etc.
I don't know. A lot more than there are companies like Apple or Google. Don't you see how many small businesses are around you when walking down a random street. Anyway why does it even matter? If only 49% of them succeeded which is less than majority, would that mean poor people cannot become successful entrepreneurs?
Of course, rich kid will not end up like poor kid, but they will be much less rich than their parents.