Hi Ben31,
In General, Yes, you can. I have made the experience, if you have a work permit, then you will have a job, so, you will have the funds to buy
yourself a ticket to fly back home. So far, nobody has ever asked me for a Return ticket.
But, i would check the conditions of your work permit! For example, the Working holiday Visa schemes need a return ticket, because they want to make sure that you find your way back home at then end of the term, and not staying "illegally". Just a "security thing".
I would recommend to take the latest bank statement with you just in case the question comes up, you can show that you have the funds to buy yourself one to get out.
Mostly you only need a Return ticket if you come with a tourist visa, which doesn't necessarily allow you to work.
Hope this helps,
regards,
lepatissier07