Nedarim 5:2

Continuing the case of two partners, if a third person was prohibited by a vow from benefitting from one of the partners, he may not enter their jointly-owned property. Rabbi Eliezer says that the person can say to the partner, “I am only entering the other partner’s portion, not yours."

Nedarim 5:3

Let’s say that a person is prohibited by a vow from benefiting from his friend, and that friend owns a bathhouse or an olive press in the city, which he has leased to a third party. If the owner retains rights in these businesses, the one under a vow may not use them; if the owner has no rights in these businesses, the one under a vow may use them. If a person said to his friend, “Konam if I enter your house” or “if I buy your field” and then the friend died or sold his property, the one who vowed is permitted. If he said, “Konam if I enter this house” or “if I buy this field” and then the friend died or sold his property, the one who vowed is prohibited.