Leaving Cinque Terre by train in April 2018. Where to rent a car before driving to Volterra?

Have you looked at picking up a car at La Spezia and dropping it at Pisa?( as you do not want to drop it at Florence)

Thank you for the quick response. After your post, I checked into the car rental from La Spezia and later dropping it off at Pisa Airport. The cost of dropping off the car at another city makes this option almost double the price of the four day rental! Car rental 4 days La Spezia to Pisa Airport = ~ $362. Car rental Pisa to Pisa 4 days = ~ $196. That is a big difference. The difference in the longer train ride on the first day is only € 9 ea. Looks like the Pisa to Pisa car rental is the better option.
We will use Volterra as our base for the four nights, and use the car for day trips through Tuscany...unless another poster has some good ideas. Thank you again. Caio!

I think you should investigate more as I've never had to pay a different city drop off charge within Italy. The companies may be fishing for higher priced sales as your dates are so far in the future. There's a fuller discussion of options from Cinque Terre here: http://www.apathtolunch.com/2015/11/where-to-rent-car-from-cinque-terre-la.html Renting from La Spezia would be far easier than going to Pisa, transfering to the airport, and then getting the bus to the car rental.

On AutoEurope I'm seeing prices from Hertz and Europcar less than $200. for a La Spezia to Pisa 4 day compact rental. (Note AutoEurope, a reputable broker, is different from AutoEuropa, a dicey car rental company in Italy.)

You should rent the car il La Spezia and return it in Florence.
Returning it in Pisa and taking the train to Florence makes absolutely no sense.
Check rates on www.autoeurope.com
If you are scared to drive into the city center of Florence, choose the hertz option and return the car on Via del Sansovino.
There is no drop off fee in Italy even if you return at a different location, as long as within Italy. Never had to pay one in my life. Not sure who gave you that crazy quote.

Rented the car from Hertz in La Spezia through Auto Europe a few years ago to drive to Volterra. We took the train to La Spezia from the Cinque Terre. From there it is several blocks down the main street to Hertz- make sure you get directions or google on line to their pick up place, they may have moved since we were there. Was very easy to do. We returned it to Orvietto 3 weeks later. As mentioned by Roberto (and he is very knowledgeable on Florence) you can return it there .

Thank you to all who responded to my question. We realized that returning a rental car on a SUNDAY was difficult, as only airport locations were open on Sundays in the area we would be near. WE HAVE NOW CHANGED OUR PLANS. Leaving Cinque Terre by train to FLORENCE for a few days. Now we plan to rent the car in Florence on a Friday. Thank you Roberto di Firenze for your advice in another post. Driving out of the ZTL in Florence seems quite easy. I actually Google mapped your instructions and "drove" out of Florence on my computer. The Hertz outlet at Borgo Ognissanti 137/R will be quite close to where we will stay, and can walk there with our luggage. After driving to Volterra for a few days and later to an agriturismo near Montalcino, we plan to return the rental car on a Wednesday in Chiusi Scalo. The rental car outlet is about a 1 minute walk from the train at Chiusi-Chianciano Terme. Then on to Rome for one overnight and then home to Canada. (We will have stayed 4 nights in Rome at the start of our trip.)
Grazie!