(a) A salary fund shall be created in the county for each district, county, and precinct officer to be known as the "(officer's title) salary fund of (name of county) County, Texas." The purpose of the fund is to pay:
(1) the salary of the officer;
(2) the salaries of the officer's deputies, assistants, clerks, stenographers, and investigators; and
(3) authorized and approved expenses of the office of the officer.
(b) The salary fund shall be:
(1) deposited in the county depository;
(2) kept separate from other county funds; and
(3) protected to the same extent and draw the same interest as other county funds.