augi, seriosly, get yourself a gold pass from the National Park Service - you can fill out the form right at the entry booth and get the card right then and there. Thereafter, all national parks, national recreation areas, and national monuments are free to you. Depending on your actual disability, you may qualify for free use of improved campgrounds - many of which have showers.
I toured 5 national parks, and eight national recreation areas/national monuments two years ago - total cost to me to enter the parks was zero, use of an improved campsite at Yellowstone and another at Mesa Verde was free. I make a habit of stopping at tourist info centers upon entering a state, to see if I can get a disability access pass to the state parks in that state. When I got home from that trip (above) I had state passes for Oregon,, Washington, Idaho, Montana, Wyoming, Utah, Colorado, Oklahoma, and Texas.
Colorado and Oklahoma also gave me fishing licenses free of charge.
You are preparing to do what I have been dreaming of. Maybe I'll see you on the road some day.