No, the law does not set a specific amount. In some cases, though rare, a court may decide that an agreement is enforceable even if it leaves one spouse with no property and no support from the other party. In determining whether a premarital agreement is enforceable as drafted, courts will examine circumstances that may have changed since the time of the marriage--such as the birth of a child, a career given up, or an unforeseen illness.

Some states will enforce an agreement to provide no spousal support, so long as waiver of support does not leave the less-wealthy party so poor that she or he is eligible for welfare. Many courts will apply broader notions of fairness and require support at a level higher than subsistence. Some states provide that the support cannot be "unconscionably" low. That is a somewhat vague term that means different things to different courts.

Some lawyers think it is a good idea for premarital agreements to contain an escalator clause or a phase-in provision that will increase the amount of assets or support given to the less-wealthy spouse based on the length of the marriage or an increase in the wealthier party's assets or income after the agreement is made.

No, but it is a good idea. Lawyers can help make sure that the agreement is drafted properly and that both parties are making informed decisions. The lawyer for the wealthier party usually prepares the initial draft of the agreement. The less-wealthy party should also have a lawyer to review the agreement, even if only on a minimal-cost consultation basis. Although you do not need to have a lawyer in order to have a valid agreement, the agreement is more likely to be enforceable if each person's interests are represented and significant back-and-forth negotiations have taken place. The agreement is more likely to be challenged if one of the parties does not have an independently chosen lawyer.