With postal charges based on size as well as weight, folding A4 letters to fit them into smaller envelopes will save you money, as will combining in a single envelope multiple mailings to the same customer or client. (smallbusinessesdoitbetter.com)
In the event of a postal service disruption, Pacific Coastal Airlines will continue to accept small envelopes and packages as cargo within our destinations in BC. (pacificcoastal.com)
None of this stuff is cheap, nor, as far as I can tell is it available in North America, but there are ideas here that demonstrate how people can share a space and still get a little privacy, a good place to work and a lot of storage in a very small envelope. (treehugger.com)