If you have any flexibility in your itinerary, it might be worthwhile considering flying in to Portland, Oregon. There are no sales or vehicle transfer taxes in Oregon and RV licensing fees are modest, based upon length of trailer. Oregon registration is also good for two years, so if you buy a used RV, odds are good that it will have a year or so left on the tags. Vehicles don't typically have any rust issues here, so it's easy to find late model used trucks in good condition. It's possible the money you save in taxes and fees could more than pay for travel costs through some of America's most beautiful country while on the way to your destination. Just a thought.....