Tex. Property Code § 82.065

The declaration may permit a declarant to maintain sales, leasing, or management offices and models in units or on common elements in the condominium if the declaration specifies the rights of a declarant with regard to the number, size, location, and relocation of the offices and models. If the declaration fails to expressly permit an office or model, a declarant may maintain no more than one unit as a model and no more than one unit as an office for sales, leasing, and management purposes at any one time. A sales, leasing, or management office or model not designated as a unit by the declaration is a common element and is subject to the exclusive use of a declarant until the declarant ceases to be a unit owner or until the declarant no longer uses the office or model for such purposes, whichever occurs earlier. A declarant may modify the exterior of a sales, leasing, or management office to conform to the aesthetic exterior plan of the condominium. A declarant who ceases to be a unit owner ceases to have any rights with regard to an office or model unless it is removed within a reasonable time from the condominium in accordance with a right to remove reserved in the declaration. Subject to limitations in the declaration, a declarant may maintain signs on the common elements that advertise the condominium for sale or lease. This section is subject to local ordinances and other state law.