An employee with a right to sue letter can file a case on his or her own behalf. This is called pro se. As a pro se plaintiff, you may also ask the court to appoint an attorney to your case, after your filing has been accepted by the court and if you can prove an inability to pay.
Remember, one of the most difficult parts of a successful discrimination case is actually filing the case with the court, citing the proper laws, and putting it in the approved format. Only when that is done correctly and is accepted can you apply for an attorney. Most courts require that you prove you are indigent or unable to pay. Commonly, this is proven with IRS annual filings or other reports.