Building a structure using a shipping container is probably going to require some serious power. The heaviest user of power is a welder. If you want to weld without access to town power you will need a serious generator.
Welders are differentiated by current capacity. An 80 amp welder can weld thin metal plate like a car body. They are relatively low current and therefore less bulky and cheaper. As the amps increase so does the price and the weight and size. The increased current allows thicker steel to be welded. According to the specification on a few machines on ebay a 150 Amp can weld 5mm steel. A 200 Amp can weld 8mm steel. Both of these have the 15 Amp wall plug. Standard house plug in Australia is 10 Amp.
A 150 Amp welder had an input requirement of 6.2 KVA (well beyond my quiet 3KW Honda house generator) A 200 Amp welder typically is looking for 7-8 KVA. This means the nice quiet, 10A outlet generators that people take camping are unsuitable.
Even my Honda 3KW generator does not have the power for weldinge significant metal.
I was guided by an experienced welder who encouraged me to buy the biggest welder practical. I purchased the Magnum 200 Amp MIG welder. I have welded a number of metal parts on the container. The roof supports are welded heavy wall pipe to 10mm steel plates.
The roof bars involved welding 4-6mm plates to the roof rails.
I suspect I might have got away with 150 Amps but the 200 was a good purchase. Making frames and welding the container walls is quite easy and the welder is running at about 50% capacity. Heavy plates 80% and the thick roof plates 90%.
My welder is on the cusp of the power rating. If I run it at 100% the generator struggles and will trip. If I reduce the power setting to 90% I can weld with no difficulty. I looked on ebay recently and found a 9 KW generator with 15 Amp socket outlets which appears to neatly cover the gap.
I used my welder a fair bit at the beginning of the project. I purchased a cheap generator to drive it. I now use it very infrequently.