One thing I missed from your post... are you intending to challenge the lawsuit?? If so, you will need an attorney, even if you can't afford one. If you are successful in defending against the suit, you will probably be able to recover the legal fees (depends on the circumstances and state laws).
As for what can happen.... if you don't show up, the Plaintiff could request a Summary Judgment against you. Or, the court could hold you in contempt if you were served to appear. And/or the Court could award costs to the Plaintiff for his expenses due to your failure to appear. A lot of possibles.
Or, if you have no defense, or admit to the complaint, you can show up on your own and enter an "Agreed Judgment". This is the probably the least expensive method since you wouldn't incur the Plaintiff's attorney fees for a trial.
Or, you could just 'no-show' through the entire process. The Plaintiff will get a default judgment against you, plus costs and attorney fees.