Richatom:
Wrt your yacht broker business (which I assume is a paid position) I think the words you are looking for are "incidental to employment". If you get paid for doing a job buying/ selling/ managing yachts, and incidentally use an aircraft and your pilots license, it's not really working for free. Somebody mentioned the FAA "holding out" issue, and "incidental to employment" is a part of that story.