How to tell if a house is vacant?

[Kent Nielson]

Aside from knocking on the door or the next door neighbor's, is there a way to find out  if a house is vacant? I know you can go to the county website and see if the mailing address matches that of the house. Assuming you find out the owner doesn't live there, is there a way to find out on-line if the house is actually vacant or if they have renters?