I work at a small company. We had fewer than 20 employees when we were AS9100 certified a year ago. Marc suggested you read the AS9100 standard. There are plenty of websites with free resources, but make sure they describe the latest version AS9100-D.
A small company can become certified, in a similar way that a single property-owner can general contract the building of his own home. But if you plan to live in what you build, you better make sure you have guidance from someone who has done this before and is familiar with code requirements for permit approvals. In our case, I asked our registrar if he could suggest a consultant with experience setting up a QMS at a small company with limited resources. We were very happy with the result and now we are being awarded million dollar contracts. We are still growing and adding on to our QMS, making improvements as we grow. We are building this house while we're living in it.