It shall be unlawful for any person, corporation, or voluntary association to solicit legal employment on behalf of any attorney, firm, corporation, or organization where the attorney, firm, corporation, or organization would not himself or itself be authorized to engage in such solicitation. However, nothing in this article shall be construed to prohibit a person, association, or corporation lawfully engaged in the business of conducting a mercantile or collection agency or adjustment bureau from employing an attorney at law to give legal advice concerning, or to prosecute actions in court which relate to, the adjustment or collection of debts and accounts only.