Moshe and Aharon had learned for the year in Israel and shared a furnished apartment. Their lease ran until the end of July, but they both had summer plans in the U.S. They sought someone to take over the apartment for July, but were unable to find anyone.
Moshe left in mid-June. “I’m leaving you $375 toward July’s rent,” Moshe said to Aharon, who was leaving two weeks later. “See if you can still get someone.”
A week after Moshe left, Aharon received a call from Levi. “Is your apartment still available for July?” Levi asked.
“It is,” said Aharon. “My roommate already left, and I’m leaving in a week. The apartment costs $750 for the month.”
“That’s a lot for one person,” said Levi. “I can pay only half that.”
“If it’s only you, I guess you can take my place for $375,” said Aharon. “But we reserve the right to get an additional person, if we find one.”
“That’s fine with me,” agreed Levi.
When Aharon returned to the U.S, he met Moshe. “I found someone to rent the apartment for $375,” he said. “At least it covered my half.”
“We shared the lease until the end of July,” said Moshe. “I should be entitled to half of what you received from Levi. Why should you get the entire benefit? He’s not using only your bed. The kitchen, living area, and bathroom are all shared areas.”
“You already left,” replied Aharon. “I was using the entire apartment myself, anyway.”
“I can’t stop you from using the whole apartment,” reasoned Moshe. “But if you’re making money on it, I’m still a partner and entitled to half the amount!”
“Consider that I simply rented him my half, in my stead,” said Aharon.
“I don’t see how you can do that,” argued Moshe.
The two came before Rabbi Dayan and related the case. “Does Aharon have to share with me the rent he received?” asked Moshe.
“Had Aharon rented the apartment to two people who needed full use of the apartment, he would have to share the rent,” replied Rabbi Dayan. “However, if he rented only his half to an individual, and made clear that it was in his stead, he does not have to share the rent.” (Rama C.M. 363:10)
“Can you please explain?” asked Moshe.
“In general, a partner who rents out a shared unit must share the rent,” replied Rabbi Dayan. “We assume he acted on behalf of the partnership.” (Nesivos 171:12)
“What if I intended only for myself?” asked Aharon.
“Even so, if you rented use of the entire unit you must share the rent with the other partner,” replied Rabbi Dayan. “Since the apartment is jointly owned, one partner does not have the right to rent out the entire unit for himself. He is effectively renting out half that is not his.” (Responsa Rashba 3:138)
“Moreover,” continued Rabbi Dayan, “even if the tenant already paid the entire amount to one partner, who acted for himself, he is not exempt from his obligation to the other partner. The other partner can still demand his rightful half from the tenant, who would then have to ask for a half-refund from the one whom he paid.” (See Gra 363:32)
“And in our case?” asked Moshe.
“Since Levi had rights only to half the use and the option remained to add another person, Aharon can claim he rented only his share, but he must clearly state that he is renting to Levi in his stead,” concluded Rabbi Dayan. “However, if he simply rented half the house, we assume he did so on behalf of the partnership and has to share with the partner.” (Sma 363:25; Beis Shlomo C.M. #48; Chochmas Shlomo 176:1; Pischei Choshen, Shutfin 4:34[65])