A different kind of yard sale

One day, while passing a nursing home, I noticed six old ladies laying naked on the grass. I thought this was a bit unusual, but continued on my way to the store.

On my return trip, I passed the same nursing home with the same six old ladies still laying naked on the lawn. This time my curiosity got the best of me. I went inside the nursing home and asked the manager if he knew there were six ladies laying naked on the front lawn?

"Yes, I know" he said. "They are retired prostitutes and they're having a yard sale."