Gas model RV's get about 6 to 8 miles per gallon. Campgrounds will cost anywhere from $20 to $50 per night depending on where you are and what the campground has in the way of utilities and entertainment... for the teens. Some places charge for showers, and everything else. Many of the Walmarts no longer let you park overnight. You will have to go to a campground every other night or so to dump your holding tanks. It's a long way to Alaska! I wouldn't let teens drive my motorhome, but it's a 39 ft with a car in tow. I don't drive it much myself! Go look at rentals, and think hard before you decide to do this. By the way, you won't make the kind of time in a MH that you do in a car. We rarely drive more than 60 mph.