Responsa for Bava Kamma 220:9

Q. A and his son-in-law B were partners in a house. A leased his half to B for an indefinite period till the latter's death, at a fixed annual rental. Subsequently, A wanted to sell his part, but B objected. The case was brought before R. Meir who sustained B's objection. Now B is seeking to sell his half and also his right to a fixed rental for the other half. A, however, objects to a sale by B of the right to a fixed rental claiming that he had originally leased his half to B for a low rental in order that B and his family live therein and enjoy it themselves, but not for the purpose of selling it to another. Is A's objection valid? Also, please note that A's daughter, B's wife, was dead, but the children she bore to A are living; does the fact that B's wife is dead prejudice B's rights? Moreover, B claims, and witnesses support his claim, that the agreement of lease was reached between A and B after a sharp quarrel which followed their buying of the property. Thus the lease was not a gift of love [in which case the purpose of the gift must be taken into consideration], but was rather the outcome of litigation and compromise and was, therefore, of the nature of a sale. B further states that should A's objection be sustained in court, he would sell his own half of the house and would dwell in the other half, or would rent out the latter half and would use the rent for his sustenance. Please further inform me, on the other side of this sheet, as to what was done in the case of the widow from Spiers and her two Levite levirs. Signed: Asher b. Rabbi Yehiel.
A. We are not to take into consideration A's purpose in leasing his half of the house to B, for various reasons. a) When B sells his right to a fixed rental to a third party, he benefits from such sale as much as he would have benefited from living in the house himself. b) Since B has lived in the rented half of the house for a long time, the transaction of the lease is by now complete so that A's original purpose in leasing it is no longer of any consequence. c) A transaction of sale, lease, or even gift, is concluded by two parties, being the result of a meeting of both minds and, therefore, such transaction is not conditioned by the special purpose or intent of one party when such purpose or intent was not in the mind of the other party. Therefore, even if B had no surviving children from A's daughter, the validity of the lease would not have been affected. d) According to your letter, the lease was not motivated by feelings of kindliness, but was a purely business transaction. R. Meir adds: Regarding the widow mentioned above, I shall order that my Responsum pertaining thereto be copied for your benefit.
The answer bears the superscription: "To my teacher Rabbi Asher."
SOURCES: Cr. 315; Am II, 174. Cf. Asheri B. M. 8, 25.