Hi Katy - my 2 cents worth, and as you are in qld;
A small
starboard go would be good as suggested, and they have been around for a while so u can probably find a reasonably cheap second hand one. They are not common in SE queensland and you might have to buy from WA. I'd imagine around $500-$800. You won't outgrow it as quickly as the Start model. I've personally used the start and Go to teach with. In my personal opinion, the start is not much good beyond the very basics and you will most likely outgrow it very quickly. The go is lighter and smaller than the start, but still on the heavier/robust side
A second hand
Bic Techno about 130 litres would be nice too. They've been around a while and should be fairly cheap - around $400? Slightly lighter but still relatively robust. A bit more common locally
A second hand
JP funster 120 - 140 litres. A newer breed of board but should be around $800 - $1100 second hand (subject to it's condition). I've personally used them for teaching and they will take you quite a long way before you need to upgrade. They are on the heavier/robust side. There are quite a few locally but I have not seen many second hand yet as they are a fairly new model. (Check with Surf FX on the Gold Coast)
A larger 130 litre
JP excite ride probably around $700 - $1500 second hand (subject to it's condition). This model has been around for the last 4 years or so and would probably be a board you keep till you destroy it because it is big enough to learn on, and continue to have fun on when more advanced, plus it will make a nice light wind board. There are quite a few of them around now in SE Queensland. It is light weight compared to the other suggestions. You can fit a JP nose protector to it if needed - the nose is where most boards take most of the beating when learning.
In general, any 120 + litre board made after 2001 will be ok for you. Some are more fragile than others and a little more specialised / slightly less stable, but still possible to learn on.
The mentioned boards are around 2.45 metres long and around 70-80cm wide. You will fit them in a small Corolla sized hatch with the front passenger seat laying back and the nose of the board pointing to the front passenger side floor, with the board upside down and the fin removed. Throw a towell over the seat headrests and just push it in. It's a squeeze but it fits
Hope this helps a bit