Two or more individuals or business entities can acquire title to real property as joint tenants.  California law will not presume that property was acquired by joint tenancy.  To create a joint tenancy requires an express written agreement.  Civil Code Section 683.

Joint tenancy has several key characteristics.  First, joint tenants have equal, undivided interests in the property.  This means that each joint tenant owns a fractional interest in the entire property, as opposed to having complete ownership of a discrete part of the property.

Second, joint tenants have the right of survivorship.  This means that, if one of the joint tenants dies, the others inherit his or her interest.  If you own property in joint tenancy, when you die, your interest in the property does not go to your children or your heirs; your interest in the property goes to the other joint tenants.  This can be advantageous; property which passes in this way does not go through probate, which can be both simpler and have advantageous tax consequences.

As a rule, all joint tenants have the same right to use and possess the property.  These rights can be modified, however, by a written agreement between the joint tenants.