The most important source of information about the rights and responsibilities of residential landlords and tenants is the written lease agreement. Some landlords prefer oral agreements, but it is more common for them to require the tenant's signature on a written lease—and a written lease protects the tenant more than an oral agreement. Be sure to read the lease carefully before you sign it.

If a tenant wants to change part of the lease, the tenant should discuss it with the landlord. If the landlord agrees, the landlord and tenant should decide how they want to word the change and then write it into the agreement. Both the tenant and the landlord should then initial the change. For example, many standard leases prohibit pets, but the landlord may be willing to accept a pet if the tenant puts down extra money as security (a pet deposit) to protect against any damage the pet might do.

A state’s landlord-tenant laws may provide additional rights and responsibilities and further define the rights and responsibilities identified in the lease agreement. These laws vary from state to state and are usually located in a state’s statutes.

In California, the written lease agreement is indeed a crucial document for both residential landlords and tenants as it outlines their rights and responsibilities. While oral agreements are legally binding in California for leases under one year, written leases provide clearer and more enforceable terms. Tenants should read and understand the lease before signing. If a tenant wishes to negotiate changes to the lease, such as allowing pets, these should be discussed with the landlord. Any agreed-upon amendments should be written into the lease and initialed by both parties to ensure they are legally binding. California's landlord-tenant laws, which are codified in the California Civil Code and other statutes, supplement the lease agreement by providing additional rights and responsibilities. These laws cover a wide range of issues including security deposits, rent control, eviction procedures, and habitability standards. Tenants and landlords should be aware that state laws may override or augment the terms of the lease agreement, and they cannot contract out of certain statutory rights and obligations.