Re: B737 Type Rating.
300ER,
It all depends on which licence you want to put it on. JARs require experience as detailed in another post. As you're from OZ, I happen to know that CASA will put it on your Aussie licence without Base Training. However, I'm not sure what their conditions are - I just know that some friends had done the A320 rating this way, but all were fairly experienced pilots.
For safety sake before you part with hard-earned cash, talk to your local CAA and see what their requirements are. There's usually a requirement to fly the actual aircraft fairly soon after a ZFT rating - something around 2 to 3 weeks I think, in the JAA system.
Also ensure BEFORE you start any type rating training that your authority will accept that TRTO (Type Tating Training Organisation) for YOU. It's often not enough to know that the TRTO is approved by your CAA, it usually has to be specifically approved for each pilot or company as does the sim on which it's being done.
The whole area can be a minefield so it's best to tread cautiously and ensure you have all the approvals needed before parting with your cash. If you're thinking of doing the B737 rating look at PARC in Ireland - they advertise on Pprune - as they use only very experienced TREs who are current on the aircraft and will give you a lot more training than just the bare rating. They also have a 100% placement rate for their graduates. The cheapest ones are usually in the USA but cheapest is often not best.
Good luck with it - it's not easy!