I take it at the moment your boss is the certifying plumber/drainlayer on your licence.  You must have a supervisor according to the Act as licensing works at the moment, so this means if your boss isn't willing to be your supervisor when you go out on your own (and I'm picking he probably won't want to be because you will become competition for him, plus the risk for him with no reward is too great).  This means that you need to have a supervisor.  Even if you do what you call non permitted work, all it will take is a complaint to the PGDB and you are facing a prosecution for working without supervision.  Remember that complaint could come from a customer, your former boss, or anyone else in the plumbing community who knows that you are not a certifier but are working out on your own in competition to them.  While this may seem unfair to you, others that have done the time, and passed the exams and are incurring all the costs involved in that i.e. upskilling, maintaining their certifying status, ensuring that the provide supervision to their own staff etc. cannot compete with you in the marketplace when you do not have those costs.

Legally anyone can start a plumbing business, BUT you must have a certifier overseeing you and so without one, you run a huge risk.  Only you can judge if that is worth it or not.  My advice is to knuckle down and do the study to sit your Certifying exams in plumbing and drainlaying and then once you have served the two years, apply for the status and go out on your own then. 

I note you said you had a pretty decent customer base outside of your bosses - remember that if you are perking without your "supervisor" being aware then you can also be prosecuted for that - plus you will have no cover by any sort of public liability insurance.   All good until something goes wrong.  Speaking of insurance, you would need to check if your customers would be covered if you went out on your own and were not working in accordance with the 2006 Act i.e. without the supervision.    Just some food for thought for you.

Ok Benny
Yes you can start your own plumbing business thats the easy bit but you will need a certifier that is willing to keep an eye on you and sign off your work. there is no law that says they must work for you though.

Im not really sure if you quite have it right though thinking you will have less stress and more money you will be working the entire time you are awake if not on the tools you will be pricing and invoicing,taxes etc and I would do some courses on small business management before even considering the step out alone. It is very common for an employee to think that they can do it better but dont see all the behind the scenes work.Also you say roofing work which will now come under LBP so you will need to be a licenced roofer to do that to.

If I was you I would
Sit your certifing Exams as soon as possible you dont have to wait to sit
find a good small business course that outlines your legal requirements as a business owner
And would suggest that you also do some study around QS to get the basics on pricing and claiming as per the building code/act

You can sit your certifying exams any time you like, but you can't pick up the certifying status until two year's after the date you became registered.  Many guys sit their exams in the two year period post registration and then pick up the qualification straight away.  Another way to ease into working for yourself, but staying legal is to perhaps talk to your current boss about contracting to him where you have some autonomy but get to gradually work into your own business.  You have all the perks of tax write offs, you have to provide your own tools, vehicle, insurances etc, but some sureity of work.  Perhaps then he would be happy to be your supervisor for the few jobs you do for your own customers.  Worth a thought - we've had a few of our staff work their way into their own businesses doing this.

Anyone who signs your ticket willhave to acknowledge you in some way to their insurance company. If they don't and you inadvertantly cause a problem, his insurer won't want to know you and neither will yours. The homeowners insurer will go after you for damages. Just imagine the worst case scenario and ask yourself if you can pay out $20k for someone elses bathroom or kitchen. I can promise you this is not my imagination.

If that scenario actually happened to you, you can bet that someone ewould compain to the PGDB and if you were licensed you would go thru the boards disciplinary proceedings and that farce would cost you another $10k

I don't doub what you say at all to2b007, but how many of these guys have ruined someones house and then tried to claim? Thats when the  problems start.