James Yaeger posted up an overview of his bug out trailer, with some shots of the inside. Lots of water, ammo and other gear, ready to roll out in an emergency.
One of these days, I will put together some variety of bug out trailer. It may be a plain-jane camper trailer with some modifications and gear stored in it, something along the lines of a modded out storage trailer or something more purpose built for traveling off the beaten path. It's a project that is still years away, so I don't have any firm plans yet, but am always interested in how other people have done their trailers.
A limitation of a setup like Yaeger's is that it relies on a generator and fuel for power, so you'll be out of luck after a week or two off-grid. I also did not see any kind of large volume water filter, though I'm pretty sure Yaeger stocks Katadyn pump filters in his bug out bags. Water purification would probably be a major task.
Adding solar panels, a 12v battery bank and a Berkey or a gravity fed Sawyer filter would allow for a nearly indefinite supply of electricity and water. Edit: In a follow-up video, Yaeger showed a Berkey filter that goes with the trailer.
This sneak peak shows a look at a more comprehensive mobile set up for long term, off-the-grid living. I haven't purchased the full DVD, but you can see bits and pieces of what they've put together inside their cargo trailer...basically a mobile, off-grid workshop/mancave.