Try gaming companies, if you put gaming chairs in them computers ETC then they will either buy/rent them of you fior quite a bit of money, its mainly down to taking there games around the country so thats why they would be interested.
I don t know about large modular buildings since people are working from home or laptop, PDA, from home or anywhere. BUT what about small buildings? Like hunter cabins? I know that it is different, but maybe hunters would pay for him to build something on their property. Not like a house, but something they could use on weekends. When you said portacabin, I though cabin. anyhow good luck. Tell him not to limit himself.
The majority of businesses requiring portacabins only require them short term and hire or lease them.
