Is it permissible for the landlord to stipulate that the tenant not host another family except with written permission?

The basic principle is the validity of stipulating any condition that does not contradict the Shariah. In stipulating such a condition, there is a legitimate purpose for one or both parties to the contract, such as the lessor stipulating to the lessee that he (the lessee) shall not utilize the usufruct himself, or that he shall not lease it except to a trustworthy person, or that he shall not lease it to a specific person. If you have a legitimate interest and a valid intention in this condition, then there is no harm in stipulating it.