Most people can't choose what they do for a living. I'd say 95% of the world just do whatever they can to see the next day.
Yes they can. It is about taking responsibility for your own actions and not blaming circumstances, bad luck, religion, zodiac sign, astrology, god, parents, siblings, UFOs, government or whatever.
Who cares about sponsors? Tennis was much better before it became just about money.
Thank god we have a free market! :-)