Responsa על בבא בתרא 84:6

A - B conceded that he was satisfied with the improvements that were made and asserted that he did not want to pay his share of the expense, but would permit A to dwell in the house. Therefore, B is required to pay his share of the expense. However, B need not pay actual cash to A, but could tell the latter to dwell in the house rent-free, for a period of time that would be equivalent to his expenditure in making the improvements.