More thoughts for your consideration.
Early this year I was indeed fortunate to pick up a vehicle for my travels at an excellent price for the age and mileage. To date I have clocked up some 23000 miles, with probably another 2500 miles in the next two weeks. The vehicle has been good to and for me, but it has also meant I had to return the favour. So far I have paid in the vicinity of $3500 on repairs and maintenance. Most of it is what one would expect, but there were one or two surprices. Which is not unusual when purchasing a second hand vehicle, despite getting good advice and mechanical check.
If you are considering a mini van, I would highly recommend that you get one with a flat floor, when the seats are removed. Put in a camping mattress, a good quality sleeping bag (I found top quality ones on Craig's List), and you are good for camping most places during at least three seasons.
By utilising places such as BLM lands, Truck Stops / Travel Plazas and free camping areas (do a web search for them), you should be able to multiply your 'free' nights, several times over. At truck stops you not only have the bathrooms, there are showers (pay) and all other facilities that professional drivers use such as washing machines and driers, and most times a microwave as well.
Keep food costs down by buying in supermarkets, and if necessary, reheating in the microwave at truck stops. Keep a box of cereal for breakfast, and buy small quantities of milk each day, unless you have a good cooler or 12v (compressor) fridge.
Don't overlook hostels. There are some which allow a free night's accommodation for three or four hours work. You can always call and ask if they do this, as I have never known any of them to advertise it.
One glaring omission from your itinerary, in my opinion, is Alaska. If you are going to do a year's trip, then surely this greatest of all States - and not just in size - deserves some of your attention.
Lifey