When the money from the land of Egypt and the land of Canaan was spent, all of Egypt came to Yosef, saying, "Give us bread. Why should we die in front of you? For there is no more money!"
Yosef refused to take any other payment for the produce besides cash. He would not take their cattle or other possessions. He had now gathered all of the gold and silver in the country into the possession of the Crown, and the citizens had nothing left to pay for the produce they desperately needed.
Now, and only now, was Yosef willing to take their livestock, as the next possuk writes: וַּיֹאמֶר יוֹסֵּף הָּ בוּ מִקְנֵּיכֶם וְאֶתְנָּה לָּכֶם בְמִקְנֵּיכֶם אִם אָּפֵּס כָּסֶף - Yosef said, "Give me your livestock, and I will provide for you in exchange for your livestock if there is no more money." Only if there is no more money was Yosef willing to make this new exchange.
Yosef had a plan over here. The entire world exists for the Bnei Yisroel, and he wished to ensure that his brothers, when they arrived in Mitzrayim, not feel like the underdogs. If all of Mitzrayim were poor like them, they would not feel inferior to them because of their lack of resources. Yosef wished to ensure that while there was still cash in the reserves of the Mitzrim, they would be responsible not only for their own needs, but also for their livestock. They would then use up their cash quickly, and all would be poor.
By the time the first year was over, the country was totally impoverished, and they had to give up their livestock for food.
When Yaakov and his sons arrived, they still had their animals intact. They had reserves of cash, and they were in no way to be considered poor. They were a cut above the locals, and their arriving from a strange land did not cause them to be looked down on. On the contrary, they were honorable citizens, respected for their wealth.
