Rashi on Genesis
ותהי הארץ לפרעה SO THE LAND BECAME PHARAOH’S — possessed by him.
Malbim on Genesis
Yoseif bought all the land. He did not wish to purchase their bodies in exchange for bread, since it is the duty of a ruler to feed his people. Only when they asked to return to their lands did he make serfdom a precondition.
Siftei Chakhamim
Bought for him. Rashi is explaining that it does not mean under his rulership, as that was so even beforehand. 21