My 2 cents worth... Shipping Containers are moderately small, need quite a lot of alterations and additions, and good containers aren't "free"... Older containers will be showing signs of rust... You'll need to treat the rust, which is kind of easy... but you'll need to keep treating the rust, over time...
However, I think a better solution would be;
- follow the shipping container principle... by building "small"...
Even smaller than this...
You don't even have to build Zone 8, 9, and 10...
You could also build a smaller kitchen (Zone 4), and push the dining table further into the kitchen, allowing to build a smaller Living Zone (3)...
Zone 1 would be the deck...
Zone 10 - The Study, could easily be your little storage shed, for surfboards, motorbike, etc... No finishes...
Or - Zone 10 could be the 2nd bedroom / rumpus area, and a storage area could be tacked onto that...
And don't build Zone 8, and don't build the 2nd bathroom.
smallhouselife.com/4910/coolest-prefab-home-by-home-depot