For instance, sometimes I've found properties that are in the condition you describe because an elderly person had lived there, but had died or moved into a nursing home. Even though the tax records may show the person still living there, the property (and the power of attorney) is being managed/handled by one of the owner's children. In another case, it turned out the property owner was in a dispute with the city. He'd moved out of town, but the tax records still showed him residing at the property.
Try your door-knocking at times people are likely to be home--early evening on weekdays, mid-afternoon on weekends. (Avoid mid-day on weekdays, if you can. Women who are home alone are reluctant to answer a door knock from an unknown male.)
Hope that helps.
Use the subject property address to access the tax records. This information should include the name and address of the owner of the property.
In most locations this can be done on line.
The "Eckler Team"