You port. If the stranger has this feature enabled (I do not), you can port to their house if they are inside by "going to location." You first have to click on this stranger before they are inside.
ravenlady is correct.
that said, it's possible that the owner of the house has the "limit home to friends" option enabled (i do). this feature is found in privacy settings and, when active, ensures that only friends can port to the house; meaning that friends of friends cannot port in.
my suggestion: since porting to random strangers' homes is highly frowned-upon, always ask before porting.