I sued my previous landlord through the magistrates office for non return of my security deposit. I won the case and he filed an appeal in the court of common pleas. I cannot afford an attorney to help me with this. I have to respond to this appeal by entering my own complaint but I am not sure how to do this. Can anyone help me??

Here is a comprehensive site - Pennsylvania Unified Judicial System.

I don't understand why you are filing a complaint in answer to an appeal.

Doesn't the Magistrate make a decision based on the appeal and your answer, if you file one? Worse comes to worse, the appeal is granted and you get another day in Court.

I'd follow that route.

What were the grounds for the appeal? As noted, an Appeal is based on some technical error by the lower court. You don't appeal just because you didn't like the verdict. So you really should have very little to do with the appeal. Its up to your landlord to prove that the magistrate ruled in error.