Has anyone ever privately built a spacecraft?

Has any small group of people of single person ever attempted to privately build a pilot-able spacecraft? I've been considering the idea for a while and wondering (monetary matters aside) would it be possible to build one legally (I live in Ireland) and if it could feasibly work. Lets say you hired a successful aeronautical engineer specializing in spacecraft and other necessary engineers and had adequate knowledge of he subject yourself, would anything (monetary matters still aside) stand in the way of the spacecraft functioning?