The person I'm looking for owes me money. They moved out of the home that I had an address for. He works for an agency which put him in different places at all times and they will not give me any information. Nothing I have any more is solid except for his social security number. I really need to find him! What do I do?

You have to file a law suit against him in court, it can be small claims if it is under the limit.
What type of agency, if it is a temp agency, or a job agency, they may be the ones paying him, so they may be the ones that would be served latter for garnishment. But they can be served in court to tell where they work.

The first thing you have to do, is get a judgement.

If you have a Judgment the Court may help you locate him.

Or are you looking for info on how to serve him?

An investigator could "probably" find him, depending on how recently he last moved, where he holds a drivers license, info along those lines.

I am trying to serve someone papers but they will not comply or come to door what can I do?

So you know where they live? Sending a certified letter they would probably refuse to sign. You have to go through the court. Calling their job I o believe is harassment