Well... "If there is no fan am I correct that there will be no electric there?"
Yes and No.
There is no electric there specifically for a fan unit. However, if there is a light close to where you are looking at putting the fan, you may be able to tap off it. I have attached the typical 12 volt diagram for your reference.
Also... Since this is NOT a factory option, doing this modification MAY void your Jayco Warranty. (has to be put out there)
22 Year Air Force Civil Engineer, Retired.. Generator Tech at Grand Forks AFB, Part time RV Tech and Parts Manager at a Jayco Exclusive RV Dealership