First, this question is improperly categorized as a labor and employment question -- it should be either in the DUI category or the criminal defense category.  In any event, the short answer to your question is "YES", your son definitely needs an attorney.  Depending on your son's age and the circumstances of the arrest, this potentially could be a rather serious matter.  The cost of an attorney depends on a myriad of factors, and varies too greatly from attorney to attorney to predict in a forum like this.  In any event, you should begin to consult with local attorneys to determine whether or not you can afford to hire on on his behalf, and if you cannot, your son should apply for the services of the public defender.