I have been operating a business under a company structure with two directors for 5 years and recently started a photography business as a hobby (it is going well too). Do I need to set up another company or can I be a sole trader so it doesn’t affect the other business?
Simple straight forward answer with limited information would be to do your photography business as a sole trader on your own ABN considering that it is not a hobby any more but a regular income earning stream for you.
For best outcome and structure you should talk to your accountant who understands your current business setup. In case you don't have one who you trust, find a CPA or CA and discuss your situation.
Hope this helps.
short answer is sure, you can trade off your own bat with the photography business.
the longer answer is you need to look at the photography gig critically and assess how to deal with issues like income tax from this business structure, losses from this structure, how does this business tie in with the existing business, is there any risk associated with the photography business, and what is at risk?
So, Anuraag is spot one when he said go see someone: that is good advice and you should take it.
Another thing to consider is how (or even if) the photography business will impact your business relationship with your existing business partners. Whilst the photography thing may have no connection of any kind with the existing business, how will this new venture impact your ability to "pull your weight" in the existing business?? Are there any potential headaches arising from someone who might think that you have taken your eyes off the road whilst you grow your photography business.
I have seen business relationships turn sour in a very short period of time when one person gets the wrong impression about something. So communication is VERY important to ensure that this cant happen to you.