Every person employed under § 15.2-1513, for purposes of salary, retirement, and other employee benefits, public liability insurance and bonds, when required, shall be considered the employee of one locality. The share of the costs of salary, retirement, and other employee benefits and expenses for the jointly employed person shall be paid to the primary employing locality by the other localities using the services of such person in the manner and amount agreed upon.

Such employment may be pursuant to written or unwritten agreement between or among the employing localities containing such other terms and conditions as agreed upon.