Originally Posted by
AK lawyer
The answer might depend upon specific terms of your contract, but assuming nothing to the contrary in there, it appears that you didn't breach the contract: a lease/purchase agreement normally provides that purchasing is an option, not required.
When did the lease end? End of September? If so, it became a month-to-month tenancy at will and he had the right to up the rent, provided he gave you proper notice. If this happened on October 1st, the effective date should have been November 1. So it looks like you would owe him two months of increased rent.
What do you mean "prorate the month"? Either you owe him for December or not, and normally there would be no ability to pro-rate the rent for that month (so as to only owe for part of the month) if that's what you mean.