>:3 <3~
Nothing so special about them, I would say, given that they are prisons. But debtors are not violent criminals, they are working off the debts they owe. Usually it's to the government, but if they owe a large enough debt to someone, that person may submit a petition the courts for a debtor's warrant.
[He waves a hand a little dismissively, because he knows of the prisons and even visited a few during his days of training, but they never particularly interested him.]</small.
You could say that a debtor's prison is more like a labor enforcement institution. You and your entire family must live there until the debt has been balanced.