Replying to Cross Country Road Trip, need car advice.

Title says it. In 2-3 years i plan on taking a cross country road trip with 3-4 others. We'll be starting in Maine, and eventually make it to Hood. I am wondering if people have advice for a van? I want it to get decent gas mileage(its a van blah blah blah) decent gas mileage for a van. and also it has to be able to last that long. And i am asking for advice now so i know how much $ we will need for a car
Thanks