I would just answer something light to let the other person know it is not a topic of conversation you wish to pursue, say something like, "I'm independently wealthy" with a smile or if you don't like that, feel uncomfortable with it, just answer "Live". I like Kathy M's responses too.

You could put a vague stop to the further questions by saying, "At the moment, I'm on Government disability" and that will probably stop the questions because you used the force of "Government" in there, like who are they to judge whether or not you are adequately disabled if the Government has said you are? And, you have the "at the moment" as it was different in the past and could change in the future. If they do try a "what did you do before" question you explain you were a student of German or some other subject you liked in school, etc. and maybe go on about what you are doing now in that vein, whether you are taking a course or thinking of taking a course, etc. and just gradually shift the conversation. If they keep insisting on questioning in a negative way; you don't really want to be talking/befriending/ed by that person do you? So you give them the look and tell them you think their questions are bloody rude and turn away.