Why does the Torah discuss Yosef's methodology in such detail?
Ramban: It teaches us, a. his integrity, inasmuch as he collected all the money in Egypt on behalf of the king, without taking anything for himself; 1 b. his astuteness, in that he did it in a way whereby he found favor in the eyes of the people, 2 even as collected all their money and their land.
Why does the Torah mention only the money of Egypt and Kena'an, and not of the other countries?
Rashbam: Either because the great distance involved rendered it too difficult to travel so far to purchase grain, or maybe the famine there was not so heavy.
Why did Yosef bring the money to Pharaoh's house only after his brothers came?
Moshav Zekenim: It was lest Pharaoh suspect that he was giving it to his brothers.
Really, he did so even before. The Torah is out of order. Refer to 47:13:1:1.
QUESTIONS ON RASHI
Rashi writes: "'By the grain (ba'Shever) that they would purchase' - ... they would give him the money." What is Rashi adding?
Gur Aryeh: "Ba'Shever" does not modify the beginning of the verse [to mean, 'he gathered the money by using the grain']. 1 Rather, it is a separate idea - "They would pay him money for the grain that they purchased; that is how Yosef gathered all the money."
Which would have implied that Yosef's aim from the outset was to impoverish the land - that was not so! The people gave their money willingly. (CS)