Always disclose anything in your possession or for which you are responsible. Many States will not respect this agreement otherwise. As a general rule, concubine agreements also cannot conclude future agreements on the children of marriage. Common law marriage is when a couple is considered legally married without the relationship being formally registered as a civil or religious marriage. A common law agreement is a written agreement between two partners who have decided to live together without being married. Common Law Partner Agreement offers both financial and emotional security. He must deal with current and future financial and real estate issues between the partners before they start living together.