A few questions:
1. At the end of Daf 11B rashi explains the Mishna regarding a landowner who wishes to take Pe'ah from his fields for a poor friend, saying that the landowner is rich; Why does Rashi add that the landowner is rich? After all on 12A we see that Rabbi Eliezer says that even a poor landowner must leave the Pe'ah for other poor people, and the Mishnah deals with the opinion of Rabbi Eliezer!? And furthermore - it does not seem that the Hahamim disagree regarding the obligation of a poor man to leave Pe'ah - althugh even if they do disagree, there is no reason to state at the beginning of the discussion that the landowner is rich!
1) Rashi must explain that the landowner is rich in order to be consistent with the words of the Gemara on 12a, "If he wished, he could be Mafkir his possessions and become and Ani ." The Gemara does not say he could be Mafkir the field and not be an owner , but that he is rich and can be Mafkir his property. Apparently, aside from the problem that he is an owner, he is also rich. Being Mafkir his property solves both the problem of being rich and the problem of being the owner.
The real question, then, is the opposite. If it is clear that he is rich, why did Rashi find it necessary to add that he is the owner of the field!
In fact, Rashi in Bava Mezia (9b) actually says that the Mishnah must be speaking about an Ashir who is not the landowner, for the landowner cannot collect from his own field regardless of his financial state. (In contrast to what he says here.) In that case even being Mafkir his property will not help for he was the Mafrish! Although we may argue, in order to answer Rashi here, that the Pasuk ("Lo Selaket - l'Ani") obligating an Ani to leave Pe'ah from his own field (Gitin 12a) does not prohibit him from collecting that Pe'ach for himself once he is Mafkir the field, as the ROSH suggests in Pe'ach 4:9, nevertheless why should Rashi find it necessary to explain that the owner is the one gathering for the Ani here?
The answer can be found in the Rash on the Mishnah in Pe'ah, who brings a Yerushalmi to prove that Rashi in Gitin is correct, since the Yerushalmi seems to interpret the Mishnah as referring to an owner of a field who wants to collect Pe'ah for an Ani.