You just park at WM overnight when you are traveling. They let you because it is 1) good business for them because you would then buy your supplies there 2) security for the stores - for free and 3) a community service to the retired travelers.
It is funny you say it is like a cruise cabin. That is EXACTLY what DSIL said when we were looking at them. DrHug decided he needs to put a When You Wish Upon A Star plaque above the headboard!

I'm all in favor of that, of course. The only thing missing will be the chefs to prepare my dinner, the waitstaff to place the napkin on my lap, and the room steward to make up my room twice a day!