What exactly is bought, when an Eved is bought: Kiddushin 6b
Whether, when dealing with legal consequences of acquiring an Eved, we need to be concerned that the master may find a blemish [Simpon] which will retroactively nullify the sale: Kiddushin 11a
Validity of acquisition, if the money paid is such a small amount as to make "partial payment" of the sum [by the eved, for freedom] impossible: Kiddushin 12a
Considering ownership of an Eved to be equivalent to ownership of Land, or of Movable Items [regarding transactions and responsibilities]: Bava Kama 11b-12b