What type of lawyer handles the secondary debt market?

[Nate Hananger]

I am in the process of potentially investing in debt (i.e: promissory notes, overages, judgments, etc.) to broaden my portfolio. Specifically buying from individuals who are owed money in various forms. I used to broker such sales before the 2008 crash so I know it can be very lucrative. 

My first step is to get some legal advice regarding how to purchase discounted debt in accordance with whatever laws apply. And then secondly, just prepping the documents and possibly having the attorney act as the escrow. Does anyone know what type of attorney would deal with such things?