I bought a 40' tall container (9-1/2' tall) earlier this year. When I was shopping for it, I was amazed at the difference in the inside temperature between a gray box and a brown box. It must have been at least 15 degrees hotter in that brown box. Anyhow, the only tall box they had was brown, so that's what I ended up with. The cost of the tall container was $2400 and the 8' boxes were $2200. I thought it was worth the extra $200.
I got it delivered for $150. The delivery was on a special roll-back trailer that made unloading easy. The driver put the container exactly where I wanted it.
I wanted to build a lean-to outside storage area on one side of the box and put in poles several months ago. I've been lollygagging around and have not finished the lean-to. Last week, we signed a sales contract on my wife's old house and we suddenly need to have everything cleared out by the end of this month. Now, I'm scrambling to finish the storage. The lean-to will be 12' wide by the full length of the container. I'm closing in 1/2 to keep it weatherproof. Since we get most of our weather from the northwest, that's the side I'm closing in. With my wife helping, it has taken us about 1 week to get the storage ready for sheeting with the metal. I'm covering the top of the container too to reduce the amount of heat inside. The top roof will overhang the lean-to by about 6' and just be a flat roof. If it leaks some, it won't matter because the container is weathertight.
I used 2x6s for the rafters and Simpson brackets on the peak. I had some brackets that are L-shaped, and I used those to clamp the 2/4 ridge down to the container. I was able to attach these to the underside of the 2" x 2" tube along both sides of the container. I am happy I didn't have to drill any holes into the top of the container. Anyhow, I've attached several pictures. I'll answer any direct questions you may have. I made good use of our Kawasaki Mule as a portable scaffold during construction.
Oh, one more thing. You have to allow room for the door hinge and swing on the front of the container. My sidewall takes a slight cant, but the roof will be square. I was able to drill into the container and use a 2x6 bolted up with carriage bolts. The 2x6 I used instead of a 2x4 because of dimensions needed. I also used 2x6 purlins on the wind-load side for extra strength.