On what grounds did Potifar merit that his house became blessed?
How long was Yosef in Potifar's house?
Da'as Zekenim, Hadar Zekenim: He was there one year - ba'Bayis in winter, u'va'Sadeh in summer. Seder Olam says that he was one year in his house, and 12 years in the dungeon. 1
Hadar Zekenim later retracted, to differ from Seder Olam. Refer to 40:1:151:1*.
Why does it say "Beis ha'Mitzri"?
Malbim: Even though he was in a Mitzri's house, which inhibits success of Hashgachah, it was blessed due to Yosef.
What do we include from "b'Chol Asher Yesh Lo ba'Bayis uva'Sadeh"?
Malbim: "B'Chol Asher Yesh Lo" includes the property he had beforehand; "ba'Bayis" is expenditures, and "ba'Sadeh" is income.
Ha'amek Davar: After appointing him over his house, he appointed him over "Kol Asher Yesh Lo." It is as if it is written 'Kol Asher Lo, v'Chol Yesh Lo', i.e. all his property, and his service of the king (refer to 39:4:152:2).