Does the landlord take the rent from the start of the contract or from the start of the tenant's occupancy?

Question:
What is the ruling on one who rented a house on an annual lease, and after a month, some individuals moved in with him, so he asked them for rent starting from the beginning of the contract, and he had previously stipulated with some of them that they pay the rent, and they accepted the stipulation?

Answer:
If one rents a house and then allows another person or other people to live with him, and their presence does not pass through the house [in a way that causes wear] and does not affect the house, and does not contradict the worship of the servant, there is no harm. He is bound by his stipulation. If he stipulated a known rent, there is no harm. If he said, "You live with me, the work is for such-and-such," the work is for a hundred, the work is for less or more, then they are bound by their stipulations. But on the condition that this residence does not harm the house. If one person rents the house and his wife, and among his wife [are] many other people, and it does not harm the house, he must consult the owner of the house, otherwise not. Because he did not rent it except to live in it with his wife, his guest, and the like. And if he lets many other people live in it, they may harm its ceilings, they may harm the water pipes, things may happen in it that cause harm. This is known by custom. If the new residents harm the house, they harm the apartment, he does not have the right to do so except by consulting the owner of the house and with his consent.