Rashi says that an eved himself can have an eved because somebody can give something to an eved on condition that the owner has reshut over it. If that is so, then why do we have to say that an eved can receive a get shichrur from the owner only because gito v'yado ba'in k'ached? We can say pashut, that the owner is giving the get to the eved by granting it to the eved without the owner having reshut over it.
Yehuda Gellman , Jerusalem
1) The Ketzos ha'Choshen (200:5 DH ul'Achar) writes that the concept of Gito v'Yado Ba'in k'Echad (see Gitin 77b) is a special Din applicable only to the husband giving a Get to his wife, or the master giving a Shtar to his Eved to set him free. This is because there is no need that the wife or Eved should acquire and own the Get or Shtar Shichrur. Since, according to the Sin of the Gemara (before Rabeinu Gershom Me'or ha'Golah introduced his Takanos) a wife can be divorced even against her will, it follows that she does not require "Zechiyah" because one cannot be Zocheh an item to somebody against his or her will. A Zechus, a merit, has to be something that the recipient wants.
2) Therefore, the Ketzos ha'Choshen writes that all that is necessary concerning the Get of a wife is that the Get should reach her hand (and, similarly, the Shtar must reach the hand of the Eved, since the Dinim of Shichrur of an Eved are derived from the Dinim of Gerushin). This is derived from the verse "v'Nasan b'Yadah" (Devarim 24:1) -- the husband must place the Get into his wife's hand.
3) In short, the Ketzos says that the Eved does not have to own the Shtar but all that is required is that it should reach his hand. Normally, an Eved does not "possess" a hand, but for the purpose of receiving his Shichrur we say that he receives his own hand. This is stated by Rashi in Gitin 77b, DH Gitah, who writes that when the wife receives the Get she automatically receives her independent hand, and it follows that there is now somewhere into which to place the Get.
4) According to this, it is not that we have to say that Gito v'Yado Ba'in k'Echad. Rather, this is the way that it works when the Eved receives his Shichrur, and no further explanation or conditions are required. On the contrary, if we would have to say that the owner must give the Get to the Eved on condition that the master has no Reshus in it, this would mean that if the owner did not specifically say this condition at the time of handing over the Get, the Eved would never go free, or, if the husband did not make a similar condition with his wife, she would never be divorced. This cannot be the case, because the Torah says that it is sufficient to place it into her hand, and no further conditions are required. So Gito v'Yado Ba'in k'Echad is an explanation for why it is enough to give her the Get, so it can work automatically without any further terms.
5) In contrast, when the Eved is trying to acquire money (with which he will buy his own Eved), all of the above does not apply. Here he really must own the money and it is not sufficient that it reaches his hand. Therefore, according to the Ketzos, Gito v'Yado Ba'in k'Echad is not powerful enough to help us in this case, because the Ketzos maintains that Gito v'Yado Ba'in k'Echad cannot effect "Zechiyah."
6) This is why Rashi in Yevamos 66a (DH v'Avdo) writes that if somebody wants to give a "Maneh" to an Eved he must say explicitally that he is giving it on condition that the master does has no Reshus in the Maneh. Only that way can the Eved own the Maneh. This is not similar to the Get, where it is not necessaary for the wife or the Eved to own the Get or Shtar Shichrur.
Kol Tuv,
D. Bloom