Вот здесь http://www.mindspring.com/~juu/maritagr.htm есть образец "Marital agreement", который заключается уже ПОСЛЕ свадьбы.

Посмотрите еще информацию конкретно по своему штату, могут быть нюансы. "A law called the Uniform Premarital Agreement Act provides legal guidelines for people who wish to make agreements before marriage regarding ownership, management and control of property; property disposition on separation, divorce and death; alimony; wills; and life insurance benefits.

States that haven't adopted the Act (or that have made some changes to it) have other laws, which often differ from the Act in only minor ways. A few states have taken the significant step of not allowing premarital agreements to modify or eliminate the right of a spouse to receive court-ordered alimony at divorce. Other states have their own quirky laws -- Maine, for example, voids all premarital agreements one and one half years after the parties to the contract become parents, unless the agreement is renewed in writing.