As for the tax side - forget anything anyone tells you about GST or ABN. GST (Goods & Services Tax) is only applicable for money earned from Australian businesses. You are not collecting GST, you are not charging GST, you don't care about GST.
ABN's (Australian Business Numbers) also only really matter amongst Australian businesses. If you were working as a contractor for an Aussie business, you would need one. However, you do NOT need to get one for MFC.
When it comes time for your tax, there is a special type of income called PSI (Personal Services Income) which applies to you. It is designed for times where you are selling your services more than an actual product. It's mostly used by artists, performers etc since the thing people are paying for is you, not your work. I had to look into for my own return this year as I was self-employed doing web design. I expected it to be much harder than it was (not that it was totally easy to work out, but once I read a few definitions of PSI on the
Australian Tax Office website, it made sense.
Also, keep track of anything which might count as an expense for camming - you will be able to claim a portion of your internet, makeup, lingerie, whiteboards, any damn thing that you use for webcam work (even if you only use part of it for camming - eg, if you buy lipstick and sometimes wear it on cam and sometimes wear it going out, you could claim a percentage of the cost).
I highly recommend getting an accountant come tax time for that - the tax office are cracking down on falsely declared expenses and I'm sure that just mentioning underwear or dildos as expenses will be enough to get your file scrutinised carefully. Much better to have an accountant lodge it, then it's their liability, not yours :-D .
Don't waste time (or money) seeing an accountant first, wait until next year. In the meantime, keep all receipts which you think might be claimable together and write on the back a good description of the item, the date of purchase and the amount since most receipts these days fade quite badly within a few months and it sucks having a bunch of papers you KNOW were claimable that you now can't read - trust me on this one.
The biggest warning I can give you is that YOU are entirely responsible for paying your own income tax. Either set aside a portion of your pay in an untouchable bank account (ie, one where withdrawals are only possible in one branch or term-deposits) or be prepared for a possibly (hopefully) MASSIVE tax bill to come later. Err on the side of caution with this - much better to have saved too much and then have extra money available than to have saved too little and face a huge debt.