Homeless Neighbor Ettiquite

This is my car on the left (with its sad dent) and the car in question on the right.

So I need some pointers on how to deal with homeless people. A homeless person, that is. A specific homeless person who is living in an abandoned car. In my next door neighbor's back yard.

Let me back up. So we live in kind of a ghetto neighborhood. No, I shouldn't be so harsh; It isn't exactly ghetto. It's...."established." Established and poor. Ok, it's ghetto. Anyhoo, when we moved in, our biggest issue was our next door neighbor's yard. He is on a corner, and we are on the other side of that corner, so his back yard is our side yard. Does that make sense? Anyway, there is only a small bit of yard between the back of his house and our driveway. A chain link fence is all that separates us. When we first moved in, his back yard was like a junk yard. Old shopping carts, broken down cars, a half disintegrated snowmobile, an abandoned camper. Two, actually. And they were both full of stinky, mangy, stray cats. And stray kittens who were cuter and less mangy, but wild. They would hiss at you if you tried to go near them. There was a bunch of other random junk back there too, including, and I kid you not, a birthday cake with only one slice cut out of it. I have no idea how long it was there, but since it was store-bought and made primarily of man-made chemicals, it seemed to be faring pretty well in the outdoors. The frosting color, a pale blue, was still discernable. Well, all this junk, as well as the mangy cats, caused us quite a bit of distress. But I'm sure the house we were moving into, which had been vacant for 2 years before we bought it, was causing them a bit of distress. Or not. Probably not. Well, we had no idea how to get them to clean up their yard. What's the nice way to say, "Hey, you're a pig and it's disgusting. Get rid of it!"? We lived with it for a while, constantly considering our options. At the top of the list was an "accidental" fire which would start on the inside of the camper and spread to all the broken down junk in the back yard. But then magically one day, before anything could spontaneously combust, the owner's son came over and started hauling stuff out. Maybe all the work we were doing on our yard was making them feel guilty. Soon the cars, campers, trailers, and cake were gone. One camper and a few other random pieces of unrecognizable metal did remain. But we felt a lot better about things. Plus, a junk tree and some Virginia creeper had started to grow up between our yards, so we didn't notice things as much.

Flash forward 3 years. The back yard next to us has started to fill up again. This time it isn't as much junk as it is the family's outdoor storage unit. The guy's kids park their unneeded trucks, cars, trailers, ATVs and snowmobiles there. At least they move around from time to time. But it still kind of irks me. Then, a few weeks ago, a guy started showing up in the back yard all the time. He always seemed to be getting stuff out of the small station wagon parked back there. I would see him 4-6 times a day, getting stuff out of the car, changing clothes. From shorts, to a shirt and tie, to hospital scrubs, and back to regular clothes. Over and over and over. And I eventually became suspicious that he was actually living in the car. I haven't been able to confirm this, as I've never seen him actually laying down in the car. But why would he keep all his clothes in the car in the backyard if he were living inside the house?

He is in his upper 20's or lower 30's. Decent looking. Well-groomed. He doesn't look homeless. He looks like someone I might have gone to high school with. Someone who might be in my ward. He might even be one of the owner's sons. But I can't get past the fact that he is either living in or living out of the car that is 2 feet away from my driveway. And why is he changing into and out of a shirt and tie and hospital scrubs several times a day??? It's all very very bizarre.

And so I need some tips. What do I say to him? "Hey, so, how's the backseat? Nice and roomy?" Or to the owner of the house maybe? "So, how's that backyard tenant working out for you?" I mean, really? WHAT DO I SAY? Or do I just skip the niceties and go straight to calling the police. I'm not sure. What would you do???