As a San Francisco Divorce Attorney a question I frequently get asked involves the rights a person has after living with their significant other (cohabiting), without being married.
When a couple live together, acquire property together, and act as a married couple without legally recognizing their relationship as a married couple or domestic partnership, this is called a common law marriage. Several states recognize common law marriage, however California does not.
Therefore, if a couple severs their non-marital cohabitation relationship, under California's Family Code, neither person accrues any community or quasi-community property rights. The case that speaks to this issue is Marvin v. Marvin (1976) 18 Cal.3d 660. Additionally, if a non-marital cohabitation relationship terminates, neither party acquires a right to financial support in the form of spousal support or alimony. However, the only way any financial support may be recognized in a non-marital cohabitation relationship is through the express or implied agreement between the parties.
Although there may not exist automatic rights for non-marital cohabitants under California law, California courts will still recognize and enforce contracts entered into by non-marital cohabitants, so long as it's not founded on sexual promises. Thus, if you and your cohabiting significant other enter into a cohabitation agreement where agreements of property division, financial support, debt division, or other provisions are provided for, courts will typically recognize it, so long as it abides by California's contract laws plus the relationship was that of a stable non-marital cohabitation.
Of course if you and your cohabitation partner decide to marry, then a premarital agreement (prenup) may be needed to replace your cohabitation agreement.
Parks Law Group is a San Francisco Family Law practice that provides legal counsel on many domestic relation issues, including divorce, alimony, premarital agreements, child custody, child support, domestic partnerships, domestic violence, marital settlement agreements, paternity, and much more.