Wash. Rev. Code § 64.34.256
A declarant may maintain sales offices, management offices, and models in units or on common elements in the condominium only if the declaration so provides and specifies the rights of a declarant with regard to the number, location, and relocation thereof. Any sales office, management office, or model not designated a unit by the declaration is a common element and, if a declarant ceases to be a unit owner, the declarant ceases to have any rights with regard thereto unless it is removed promptly from the condominium in accordance with a right to remove reserved in the declaration. Subject to any limitations in the declaration, a declarant may maintain signs on the common elements advertising the condominium. The provisions of this section are subject to the provisions of other state law and to local ordinances.
RCW 64.34.256