Can an ADU or JADU be used as a short-term/vacation rental?

No. Generally, J/ADUs are not allowed to be rented for less than 30 days. This discourages the listing of ADUs on popular websites like Airbnb and VRBO and promotes them as a means to increase housing stock for the diverse needs of county residents. Some cities may require you to file a deed restriction agreeing that the unit will not be used for short-term rentals.