Nothing prevents unmarried cohabitants from leaving estate property to the other partner upon death in a will. Alternatively, intestate succession laws may not provide that any of the property will pass from one cohabitant to another, since intestacy laws are limited to marital and other family relationships. A fellow cohabitant might be able to get a share of the intestate's estate by arguing that the parties entered into a financial or property-sharing arrangement, though such claims are often difficult to prove. A will is generally the best method to ensure that a partner's property is given to the person he or she designates.

Another complicated situation can arise if one cohabitant is disabled and requires a guardian. To ensure that one partner is named guardian or is otherwise able to make decisions for the other partner, the parties can prepare a document providing durable power of attorney to the other partner. Under this arrangement, the person granted durable power of attorney could make healthcare decisions for the disabled person. Similarly, a party can draft a living will (also called a healthcare directive) that dictates the wishes of the party regarding life-prolonging treatments.