California Family Code section 1612 lays out what can and cannot be included in a premarital agreement. The most important issues in just about any premarital agreement are the property rights of the parties and whether or not there are any limitations on spousal support.
Yes and no. Many times, if a party is just trying to protect what they already have or protect the separate character of a future inheritance, a premarital agreement may not be necessary. This is because even without a premarital agreement, property acquired prior to the marriage is the separate property of the acquiring spouse. Property acquired by inheritance or by gift is also separate property, even if it is acquired during the marriage. There are still some pitfalls to be wary of here.