Astrid, I tried to follow your link, but I got errors...

I'm not so much bamboozled by the IT side, but the business/legal side of it?
ABNs - can you earn up to a certain amount before you need one?

How do you register as a business, and does that necessarily mean you can purchase
things wholesale? Is this up to the wholesaler?
I think it is, as DH works in wholesale sales, and his company won't allow you to purchase unlesss you have aphysical shopfront, not just an online store.

Isn't there some sort of legislations that if you earn under a certain amount
from a "hobby" you don't have to declare it as taxable income? I know tupperware sell themselves under this guise..

What else do I need to be aware of?