Save yourself a lot of time and money by buying an INSULATED shipping container. They are highly efficient, and just as easy to modify as the regular containers....the one caveat being you can't use a torch to cut holes because you would set the foam insulation afire.
Sawzalls are my friend...
Another thing to keep in mind is that since containers are modular, they mate and stack well. You could just as easily set up four (4) of them with an inside atrium or courtyard, and the outside having only the access door(s). That improves security if you haven't bermed around the buildings: you get light through the courtyard windows, no other easy ingress.
Berms are nice for thermal efficiency, but allow easy access to roofs and stove pipes/vents. Bunker-busting tip: drop a grenade in or just stop up the stove pipe, and the residents tend to come out like roaches.
Cut off the doors from one end of one of the containers, and re-set it somewhere else on the building. That way you can put a set of 'garage doors' where you want them to lock in your vehicle(s). Modify the door latches to work from the INSIDE, swinging OUT.
And being modular means you do not have to do the whole thing at once. Set your first basic unit, and add to it when you can.
With proper anchor points and a good (set of) winch(s) you can place 'em exactly where you want 'em, if they dropped them in the wrong position.
If you stack units, have a crane out there with more than adequate capacity to do the lifts, and get them ALL lifted at the same time. Getting the crane out there more than once is expensive.
Two 20 footers and two 40 footers will give you a courtyard about 20x24. Four 40-footers will give you a yard 40x24...and so on, depending on how you arrange them.
Google is also my friend, in this case with general container info:
http://www.containeralliance.com/buyers-guide.phpYou'll obviously have to check local prices for cost and delivery.