Aryeh and Chaim shared a two-bedroom apartment. Each of them used one room.
Shortly after Aryeh went away on vacation, Chaim’s cousin Shlomo called and said, “I have a conference near you in two weeks. Can you suggest any reasonable accommodations?”
Since Aryeh was away, Chaim suggested Shlomo sleep in his room. “It will be nice, and you won’t have to pay for a hotel,” he said. So Shlomo came to the apartment, taking care not to upset any of Aryeh’s belongings.
A few days later, Aryeh called the apartment, and Shlomo answered the phone. When he learned that Shlomo was staying in his room, he said angrily, “Chaim had no right to let you use my room. If you continue sleeping in it, you’ll have to pay me $50 a night, like a hotel.” He then hung up.
When Chaim returned that evening, Shlomo related what happened. “Aryeh tends to get excited,” said Chaim. “What’s it to him that you’re in his room? You have only another two nights.”
When Aryeh returned from vacation, he confronted Chaim and demanded that Shlomo pay him $50 for every night he stayed in his room. Chaim thought his demand was silly, so they approached Rabbi Dayan. “Does Shlomo have to pay me?” Aryeh asked.
“The Gemara [Bava Kamma 20a] says that a person who benefited from another’s property without permission without causing any loss is exempt, post facto,” replied Rabbi Dayan. “The classic example is a person who dwelled without permission in the property of a second person who never intended to rent the place out. The rule is called ‘Zeh neheneh v’zeh lo chaser – This one benefits, and this one doesn’t lose'” [Choshen Mishpat 363:6]
“However, the Tur writes that if the owner told the dweller to leave, the dweller is liable for every day he stays after that point,” continued Rabbi Dayan. “We cannot force the owner to grant permission for the person to stay there.
“Nonetheless, Minchas Pittim [363:6] writes that if the owner had no possibility whatsoever of renting out the property, the dweller is not liable to pay anything – even if he was told to leave.” [Pischei Choshen, Geneivah 7:10(35)]
“What if the owner said, ‘If you don’t leave, you’ll have to pay me $50 a day?'” asked Aryeh.
“If the dweller did not agree to pay this sum, we cannot construe his silence as agreement,” replied Rabbi Dayan. “We view him as a person who dwelled somewhere without agreement, and he pays the going rate. The same is true according to many authorities if the owner never told the dweller to leave, but warned him that he would have to pay.” ([Erech Shai 363:6; Tashbetz #174; Pischei Choshen, Geneivah 7:19]
“Thus,” concluded Rabbi Dayan, “Shlomo has to pay the going rate for such a room for two nights.”