Dave, you do not buy the notes at the courthouse. It is the place to go to learn about the notes (actually the trust deed that the note is attached to) and how they are recorded, and the terminology and how to recognize who is who. You then locate the noteholder to see if they are willing to sell.
This will also give you a data base of most all people (and banks, if you choose) that own notes and buy notes in your local area.
All leads come from those records, even the ones that you buy (leads) if you go that route because these companies have people (or programs) that scour those county data bases for the information that they can sell to others.
If you learn how to do this yourself, you will begin to notice when someone did not do things correctly, which demands a larger discount because you buy the note then correct the mistake.