IDP has nailed it. You can look at Britain to see where this whole squatting movement goes. I read an article a year ago about a London man who went on a vacation for a few weeks and came back to find his own home "Occupied". And the government sided with the squatters. The man and his family were forced to take up residence elsewhere while they go through the legal battles.
I am seriously considering getting some sort of gas and some sort of RF trigger and then hiding the canister in the main air duct plenum. When I leave for an extended period, I arm the device. If I come home to find my home occupied, a quick RF signal and the house fills with gas - lethal or non lethal. I then don a mask, and remove the bodies. I don't know officer.. looks like they suffocated. Do you think I have a CO leak somewhere? We better get out of here till I find it. Heck, I can probably just rig something that pumps the exhaust from the furnace into the ducts..
I may also take to leaving poisoned bottles in the liquor cabinet. Oh, did you break into my house, find poison and ingest it? Too bad. My invited guests all know to look and make sure it doesn't have the little hash mark on the top...
This happened all of the time during WWII in Europe - people would evacuate and the return to find their home occupied. Where was the deed? In the house of course. Part of your bug out pack should include any deeds to your property - with copies stored in other locations.