For the purpose of facilitating the recruitment of professional and technically trained persons to fill positions for which there is a shortage of qualified applicants, a county may expend county funds to pay reasonable travel expenses of applicants for county employment in traveling, from any point within the continental United States, to and from the place or places at which the applicants are to be examined or interviewed. Such payments shall be authorized only upon a determination by the board of supervisors that the expenditure is necessary to recruit qualified persons needed by the county.