Why does the Torah interrupt the dialogue between Lavan and Yakov with a description of Lavan's daughters?
Rashbam: To explain why of Lavan's two daughters, Yakov wanted the younger one. 1
How do we know that Yakov worked for Lavan during that period - since no mention of it was made until now?
Seforno: Refer to 29:14:1:1*
Ramban #1: It seems that, from the moment he encountered Rachel by the well, where the Torah records (in Pasuk 10) "and he watered Lavan's sheep", he continued to do so, to spare Rachel, whom he loved, the onus of doing so.
Ramban #2: Yakov initially stayed with him as a guest. However, after a month passed and Lavan saw that he was living off his kindness, he tricked him into working for him by flattering him. He told him that the man of ethics that he was, he would never agree to live off somebody else. He would therefore be bound to volunteer to work for him - not for nothing of course... .
What did Lavan mean when he said "Hachi Achi Atah va'Avadtani Chinam"?
Rashi: 'Despite the fact that we are brothers it is not proper that you work for me for nothing'.
Tosfos ha'Shalem (1, citing R. Efrayim): It is proper that you work for me for free, for we are brothers. However, I do not want this. 1
Bechor Shor: Since we are brothers, it is a greater evil if I do not pay you properly.
Oznayim la'Torah: Having ascertained that Yakov was his equal in swindling, 2 Lavan was afraid that Y'a'akov was working for him free wwith some trick or other in mind, so he offerred to pay him before he succeeded in tricking him.