They cannot take legal action against you unless you have signed for his credit cards.Just because they have your address does not mean you are responsible for his debt.
Call Legal Aid and tell them your problem.
Look in your telephone book for the telephone number. If you cannot find it then call your operator on the telephone and ask for information. Tell them you want Legal Aid Office telephone number.
If you cannot get Legal Aid office then call an attorney in your town and ask him.
The obvious answer is medical law, and employment law classes. What classes are available in each field will depend on your school. A hybrid of those would seem to fit best. Perhaps even talk to the professors in that field and see if you can get paid to do research from them (wait till you are done with your 1L year to ask). Additionally I am sure your law school will have advisers who know about the area of law and can recommend what to take.
My advice to you though is to keep you options and mind open until you are done with at least your 1st year required courses. You may find once you start to study that you don't want to practice that type of law and instead want to focus on something else. Just keep an open mind, maybe you will end up at the same place but maybe not.