For want of any definition, may I suggest that if you make enough money out of aviation / aerospace to consider it a significant part of you income, you are a professional - regardless of what job you are doing in that.
Well, I probably barely cover expenses...but without instructing/aviation writing I'd be spending huge amounts on helicopter flying, so I'd have far less disposable income (like none or a minus figure
) so in that sense it qualifies as a significant part of my income.
