The chances that you become a tenured professor are between slim and none. Getting into a top notch graduate school gets you through one filter but there are not nearly enough tenure track positions for all the graduate students graduating from top notch graduate schools, let alone all graduate schools. Becoming a tenured professor is not a career path any more than becoming a professional athlete is one.
If you or your family need to borrow money to chase this dream, re-think your plans right now. If, on the other hand, the cost of education is not a big deal, feel free to chase your dream and enjoy the experience. After all leisure is the basis of culture.