I encourage you to use the car you have now first, assuming it's paid for. Pull the back and passenger seats, build a sleeping deck, etc . Lots of people do that.
I also am on disability and was wondering if any of you can let me know the best way to keep an address for social security. Will a po box work? I plan on slabs in the winter and staying in ca in summer just in cooler place.
I assume you already have direct deposit set up or are using the US direct express debit card, and that you will be able to access your funds wherever you are.
There are two different address we need to worry about.
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legal residence - the feds (and others) will require you to have a residence or "physical address". If you currently have a physical address I would use that going forward. You don't actually have to live there anymore since you are nomadic. And it is likely already on your DL.
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mailing address - you could use a PO Box, but you usually have to show a DL
and a utility bill or similar. And you'd have to change your mailing address with AR DMV, SS, etc, every 6 months when you moved from place to place. And forwarding the PO boxes to each other as you move won't work as a great deal of federal mail is marked DO NOT FORWARD.
For the same price as a PO Box you can hire a mail forwarding service to be your mailing address. They'd collect the mail and send it to you wherever you are. The cheapest I know of is
My Local Mailbox in San Antonio, $10/mo for the base service, plus the cost of postage they incur on your behalf. If you can find a cheap service like that in AR I'd use it so the mailing and residence state matches.
With these two addresses in place you can look like a typical homebody to the institutions but live your life on the road.
Good luck, brother.