Sam, if you definitely intend getting one (or 2) get your tank and bits sorted out first. You should be able to get tanks fairly cheaply 2nd hand on TM or Trade & Exchange (they're way cheaper in Auckland). Cycle your tank before you get your axies. See:
http://www.caudata.org/cc/articles/cyclingEDK.shtml
You can make caves/hidey holes out of terracotta pipes/pots or bricks and/or pvc pipes...etc. If you go for sand option for substrate, you can get a 25kg bag from landscaping/garden place (or Bunnings) for $5.
Jennifer Macke posted another thread about permanent sand substrate here, which is good:
www.caudata.org/forum/messages/793/77098.html?1169876760. Another axie owner, can't remember who, did something similar but using gravel pieces embedded into the silicone at the bottom of the tank.
Axies are priced, at petshops according to age/size. The smaller they are, 3-4 inches (approx $25) to adult sized 8-12 inches ($45); though they maybe more expensive in Auckland. There are a few breeders round top half of North Island, that are selling axies from $10-$50 (depending on type - goldens sell higher end of the scale); but also some further south that are willing and quite used to shipping axolotls round the country at a reasonable price.
You may even find that someone wants to sell axolotls, tank and whole setup which could make it quite cheap for you (my sister bought four of her axies with complete tank/decos/gravel /filter setup - 2 3ft tanks for $60-$70 a piece total - tho she used sand rather than the gravel provided)
