What a curious career! Trades in general, and plumbing in particular, seem pretty lucrative, particularly where I am (Sydney - we've had a crazy property and construction boom). And the path to small business ownership is fairly well trodden.
I'd say most 'entrepreneurs' are probably in trades, we just don't just that word for some reason.
I'd say most 'entrepreneurs' are probably in trades, we just don't just that word for some reason.