On the description of the stalls, it says they are Free stalls, but when you actually click them the charge is 10 gpm to claim them.
I have also experienced, on at least one stall, that upon hiring it you keep it until the next reset.
Quote from: "Fun with Words"Free; See also - Unused, Unoccupied.
<_<
It's still not clear enough, then. I didn't read it that way at all.
Replace 'free' with 'available' and there you go.