Craig,
Assuming you get E-Jet or B737, you should get two options, which will be outlined in your letter of offer:
You can pay up front (no benefit unless you are prepared to take the risk of claiming the rating on tax), or salary sacrifice the rating over one or two years.
The one year option is the same price as pay up front, where the two year option has a surcharge applied. I can't remember the exact amount, but I think it was about 10% of the total amount.
The only direct expenses when you join are your living costs (if you happen to live in a city different to where you complete the endorsement).