I imagine your brother will be quite tired from a trip like that. It is true that taking NJ Transit to Septa trains in Trenton is the cheapest route. But, for just $41 or so, your brother can just take an Amtrak train from NY Penn Station to Philly's 30th Street Station---no need to change trains. In order to get to Penn, he can take an airport bus to the A train subway ($2.00 for Metrocard) which goes right to Penn Station. Or he can take a taxi which charges a flat fee of $35 plus tolls (4.00 for the midtown tunnel) & tip.

As for renting a car, after a trip like that, I don't recommend it. It might take him an hour just to drive on the Belt Parkway alone in order to get to the Verrazano.