When Toni and I went from Florida to New York on the inter coastal waterway we left our truck & trailer in Ft.Pierce Florida in secure parking at the marina. We had thoughts of renting a car one way back but after some research we found it would be extremely expensive. We met our now good friends, the Vinroots, on the Potomac River in Virginia and made plans to return to their home. We intentionally missed some sights as we continued north to New York so we could see them on the return trip. We left the boat at their dock and they took us to the train station in Richmond, Va. where we took the 19 hour trip to about 80 miles from Ft. Pierce. We then rented a car, retrieved our rig, and made the return trip to get our boat.
Toni informed me I will be traveling alone on any future 19 hour train trips ( I should have got a sleeper). If we plan a future trip I think we would make arrangements to start and end our trip in cities with airports or train depots. It might be economical to rent a pickup from U-Haul one way. A rental car from New York to Florida would have cost us more than airfare because they have to pay someone drive the car back and then get the driver back.
We were on the boat for six months, 3 1/2 on the water and 2 1/2 on land. Your solution may vary depending on the length of your trip, the time you have, and your budget. You came to the right place for answers, good luck in your research and enjoy your cruise.