I've seen schematics/floor plans of something like these, but not a detailed view inside. Asking price is $30K for the pair - while these aren't posh, if you think about what it would cost to build something like these new, it's a pretty good deal.
Since they're much tougher than your average shipping container, they would fare better underground if you were trying to build some variety of doomsday bunker. One of the operations that specializes in bunkers/storm shelters could almost certainly help with burial and constructing some access tunnels/hatches.
Even above ground...one would need a plasma torch to get into them.
Wouldn't need too much work to get 'em ready to operate. Fresh coat o' paint on the outside, some maintenance on the outside and you'd be good to go.