Take a look at this Double Wide Trailer!
I was browsing YouTube and found this video about a trailer that was being sold earlier this month. If you watch this clip it will give you a good idea as to what a very typical commercial modular building looks like. Most companies in the modular building business have trailers like this available for rent or purchase - new or used.
If you are searching for temporary or long term space a modular trailer like this is probably a very good option if you have the location to install one.