What legal association does someone who holds property for someone else?

If you hold personal property of someone else, without payment, it can be called a "bailment" in which you are the bailee and the property owner is a "bailee". You may also be a trustee of a constructive (implied) or actual trust in which you hold property that belongs to someone else. For example, if you find valuable property, you are a constructive trustee of the owner and have a legal obligation to return the property upon demand by the owner. Furthermore, you could hold someone's property "in escrow", pending completion of some event. There are other similar arrangements, depending upon the intent of the owner and the possessor.