In the majority of states, you are permitted to be represented by an attorney in small claims court. In some states, attorneys are allowed only if the judge consents, and in other states attorneys are required if the party is a corporation. Some states don't allow representation by attorneys at all. (See the Appendix for your state's rules.)
Even in states that don't allow lawyers in small claims court, it is still perfectly legal to get an attorney's advice about your small claims case.
Many states forbid the use of small claims court by "assignees" (a fancy term that usually refers to collection agencies). In other words, in these states you cannot hire someone to sue for an unpaid debt. But the majority of states still allow suits by collection agencies. Check with your small claims court clerk for information.
Attorneys can always bring suits on their own behalf. Even in states that don't allow attorneys to represent someone else in small claims court, attorneys are allowed to sue on or defend their own claims.