My wife and I bought gallons and bottles of water for all 3 tenants so they could at least have a drink and brush their teeth.

@Joe Splitrock The fence belongs to the house next door.

@Jessica Vollendorf Lets meet at the Gold Dust Meridian on SE Hawthorne, if you've never been there they have the longest happy hour in PDX 2 - 8PM everyday, great drinks and appetizers are outstanding as well. http://golddustmeridian.com/I can do anytime after 5:30 but 6:30 is really good. 

Could it be that I do have a private spring, but that in the past this huge Oak (5' behind my house with branches almost to the front of my house and thus roots as well) was drinking all of the water?

A refrigerator close to the door makes grabbing a drink or meat for the BBQ an easy task.

The house belongs to a father and a son.

She explained at the time that none of the utilities were on and she still had quite a few of her belongings in the house.

You will have to evict.I would offer to assist in moving his belongings to a storage facility and put his butt on the curb if I could.

Look for estate sales which are where they sell the belongings of a recently deceased individual.  

Last thing you want is to be liable for all of their belongings inside the home (an unexpected amount), in case of a fire!