If you log off while having a stall rented, it would become permanently rented until next restart...not sure if you have to log off in the same area.
..not sure if you have to wait logged off for some time
(maybe for the rent time to end) or if it works just with relogging.
character: Defewe Rydl
stall: House of Trade, the one closer to herbalist Naryldor De'alow