My wife was allergic to cat hair, breaking out in a rash wherever she was touched, so we've been a multiple dog house for years.
A 4-5 month old cat showed up on the side porch, rolled on his back, started softly mewing and began kissing my wife's toes. Hot day, over 90. "I'm letting him stay in the hallway .. but nowhere else," said my wife, as she put down food, water, and a litter box.
After two weeks of searching for posts about a lost cat matching his description, and turning up nothing, the cat was given free reign of "only the front half of the house," where he started mounting sneak attacks on our dog's tails from behind a curtain as they walked by ... like Cato, who'd launch the same stealthy attacks on The Pink Panther at any given moment.
That was two years ago. Now he naps on the bed. And my wife got over her allergy.
We have a dog door they can all come and go out of to the fenced area of the property. He was putting on more weight than the food we were feeding him would indicate. Sure enough, he was mooching treats and food off of a couple of neighbors. And become as much of a food nut as one of my big dogs is (starving when he was rescued from a bad situation).