I know this topic is a bit stale, but ..... I'm doing some renovating of my own up here and one of the "options" I have for creating space is a couple of twenty foot long cargo containers (aka: sea cans). These, if able to be moved are classified as "temporary" in every sense of the word, are lockable, weather tight and transportable on your average tilt-n-load. A twenty footer is 160 sqft. (20x8 foot print)
Any reason why you couldn't put in a pair of these ..... say about 10-15 feet apart, build a shallow pitched truss, tin-clad roof to cover both containers and the space, but make the roof in say ... four parts so that an average excavator could lift it off in sections if necessary, and then put a deck under the open air covering?
Build your offices inside, with quick-disconnect power cabling and put a front door just inside each container door so that at night you swing the container doors closed and drop in a padlock.
Anyway ... I was just daydreaming about this recently so I thought I'd share my idea for "temporary" under 200 sqft per unit.
cheers