tracking a criminal down electronically
mojonixon: 1. real estate brokers are typically state licensed. State licensing boards often have online databases with good contact info.
2. he probably owns real estate. if you can narrow it down to a county, check that county's property records (also often on the net). Nexis/Lexis or Westlaw also has decent nationwide searches.
3. some counties also keep records on personal property, i.e. cars. he's probably run to a relative, is his car in their driveway? 
4. +1 to the previous recommendation to send him an email containing a link, to get his IP. 
5. zabasearch for established addresses (does he have a second home? relatives?)Frankly, this type of thing is a lot harder than it seems. Although, law enforcement should be able to run his social security and credit card numbers to find him. Once he settles somewhere and his new info has time to get into the "system" it will be easier for you to find him.