Tex. Local Government Code § 292.003

(a) The commissioners court of a county may provide, maintain, and repair a branch office building or a branch jail in a municipality with a population of 15,000 or more, other than the county seat, in the same manner as the court may take those actions at the county seat. The commissioners court may finance those actions through the issuance of bonds as provided by Subtitles A, C, and D, Title 9, Government Code, or through the issuance of evidences of indebtedness in the same manner as evidences of indebtedness applicable to a courthouse or jail at the county seat. Taxes may be levied for the bonds or evidences of indebtedness in the same manner and subject to the same limitations applicable to a courthouse or jail at the county seat. The cost of the facility may not exceed two percent of the taxable value of the property in the county in the previous year. The commissioners court has custody of and shall care for the facility.

(b) On provision of a facility under this section, the commissioners court may allow a county officer, except the district clerk, a county or district judge, the county clerk, and the county treasurer, to maintain a branch office and provide deputies in the municipality where the facility is located, in the manner authorized by Sections 292.024, 292.026, and 292.028. The commissioners court may limit the authorization and maintenance of branch offices.

(c) A county officer shall keep the original records of office at the county seat.