JSD-

I usually walk through 30th St. Station every morning after taking a regional train to work, so I can sort of help with your question.

I've never rented a car from this location, though it's fairly easy to find. When your train arrives, head towards the 30th St. side of the station (one side meets 29th St.). On your right should be a small walkway that goes slightly uphill. This walkway goes towards the station platforms where SEPTA regional trains depart/arrive.

The Hertz location at 30th St. is located at the beginning of this walkway, just to right. The north side of the station which has the rental car office also has the Amtrak ticket windows, which are on the 29th St. side (east) of the station.

Like I said, I've never rented a car from here, but it seems straightforward for the rentals and returns.