Apparently the house that Rick Santorum owns in Penn Hills, PA is now vacant (it was previously rented out to family members). However, you shouldn't try to confirm that yourself because the police have stepped up patrols in the area of the house based on reports of trespassers.
Here's the story from KDKA-TV
“He doesn't live here,” said Ed Vecchio of Penn Hills. “The house he's registered to vote out of, is vacant -- no curtains, furniture, nothing in there. It's abandoned for over a month. So, I feel it's my right to contest his vote.”
Those comments from the husband of the head of the Penn Hills Democratic Party led police to beef up patrols around the home of U.S. Senator Rick Santorum.
The increased police presence began late Tuesday, after authorities in Washington D.C. contacted Penn Hills authorities.
U.S. Capitol Police received a complaint from Karen Santorum.
She was worried that someone was trespassing or prowling on their Penn Hills property.