Is a Patent Attorney required for filling a patent application?

I have researched an idea and thinking of patenting it. I have googled it and found out how to file it online. So should I file it online or should consult an attorney. The attorney would cost me money, but online filling won't cost much. But I'm not finding it safe to fill it online. I told this to my friend, he stays in Sydney so told me to refer [Cotters](http://www.cotters.com.au/registered-designs/) to register my design. Can anyone please suggest me what to do?

I'm very confused...