You can convert a shipping container to be liveable. It takes a good chunk of work though. That said, many migrant living conditions are not in good enough condition to be considered legal. Gebbers Farms here in Washington was “fined” over $1 million for not having liveable housing for their migrant workers. Fined is in quotes because they worked out that they would spend over a million on housing and pay a $10k fine. So they worked it out that pretty much all they had to do was build the housing they fucking should have in the first place.