Well I reckon turning over $19,900 doing websites (even tho under the $20k) would be classed as profitable and you're most likely to be setup as a business. I'd be wary of some accountant's advice too

I worked for an accountant for 9 years and we've shared the same floor with a few dodgy ones who will tell you what you want to hear.. ie.. you don't have to pay tax.

From that link:
Does your activity have a significant commercial character?
Very important question. Invoicing people for work carried out is pretty commercial regardless of the turnover.

Definitely ask an accountant, or even a couple of them! Ring the tax office too if unsure. They can help determine hobby vs business better than an accountant.