For a start you will need a Coxswains Certificate, that allows you to charter up to 12 meters enclosed and partial coastal waters (in nsw).
As others have said, getting the boat into survey would be a nightmare, especially if it wasnt built to survey in the first place.
However, given your experience, you could simply get your cox and sailing instuctors certificates and work for a school
or other charter co. The pay rate is pretty ordinary, but you get paid to go sailing all the same.
Having said that, there "used" to be a difference between charter vessels and sailing school
vessels. Sailing school vessels werent subject to the same scrutiny- as they were controlled by Yachting Assn NSW at the time. That was ten years ago when I managed to get my RL24 registered as a Sailing School vessel, but not as a Charter vessel.
I would suggest you not only contact the Roads and Maritime Services, But also YA NSW, though my guess is that things have changed over the years.