lists of absentee owners?

[Ki Lee]

On J. Scott's "The book on flipping houses"  He mentioned that there are many services that can provide lists of absentee owners where the list can be filtered by location, amount of equity the owner has, and the amount of time the owner has held the property.  Where can I find this? 

Also, the same book mentioned using sites www.census.gov and www.bls.gov to look for population trends.  Specifically, I wasn't sure how to navigate www.census.gov site.  If I want to check the net migration of a particular city or neighborhood, where would I go in the site?

Thanks in advance