When two people want to leave their property to each other when they die, this can be accomplished by creating a joint will. For a couple (or any two adults) to make one will instead of two is legal and the result is enforceable, but it pays to consider the downsides before jumping in.
Last Wills and Joint Wills
Every will is a legal document that sets out who is to inherit property when the person making the will (the testator) dies. When two people make a will together, leaving all of their property to each other, it is called a joint will. The document also sets out who is to inherit when the last of the testators dies. Unlike a regular will, a joint will is treated as a contract between the two parties. A regular will can be revoked at any time before your death, but if you make a joint will, both testators must agree to revoke it.
Making a Joint Will
The same rules apply to making a joint will that govern making a regular will. State laws differ, so it's important to find out and follow your state's rules about making wills. Generally, you only have to identify yourselves, name each other as sole beneficiary and describe who is to inherit the property after both of you die. In some states, you must explicitly state that the joint will is intended to be a contract that binds both parties and is not revocable after the death of the first, but in many states it is presumed to be an irrevocable contract without such a statement. The number of witnesses required varies among states so be sure to find out before you sign. Legal help is not necessarily required, but an experienced attorney can answer your questions and make certain that your will expresses your desires.
Advantages to a Joint Will
A joint will is a simple and neat way to deal with an estate. Both testators can easily understand where the property is to go, and there are no ambiguities. Another reason people choose to make a joint will is to make sure that a third person or persons -- selected by both testators -- gets the property when both testators are dead. If a wife dies with an individual will leaving everything to her husband, he could then remarry and leave his property (and the property he may have inherited from her) to a new spouse. A joint will prevents this from happening.
Disadvantages of a Joint Will
The disadvantage of a joint will is the same as the advantage: it locks in the surviving spouse even if circumstances seem to dictate a change of beneficiary. For example, imagine a joint will made by a couple leaving everything to each other and, at the death of the second spouse, the remainder goes to a poor relative. The surviving spouse inherits, and a year later, the poor relative wins the lottery and doesn't need financial help. Or the relative commits a crime and goes to jail for life. Regardless, the will cannot be changed. Because of the downsides to a joint will, it pays to discuss alternatives with an attorney or financial planner before writing one.