Some ideas and prices:
Studio backdrop paper ("the real thing") - 9 feet wide, comes in rolls - $95 at Ruby Photo, $85 each if you buy two rolls. You can use a bamboo pole and drill a couple of holes in your ceiling to mount ceiling hooks, like what I've done.
Curtain material from Spotlight. About 1.5 metres wide, any length you want. can even ask them (or your longsuffering mother) to sew it together for you to make wider backdrops. They have some nice "painted background / stonewash" patterns available. Cost from $15 per metre upwards. Try to bring it home on the cardboard roll, which they will give to you for free, because if you fold it up to put into a plastic bag, you will have to iron out the creases later.
Reflective plastic sheet backdrops can be had from those shops making awnings and tents in the industrial estate around St George's Road (off Lavender Road). About 2 metres wide, $7 per metre, VERY heavy. Same thing - ask them to give you an empty cardoard roll rather than fold it up. In any case you can use the cardboard roll to put up the backdrop by using a bamboo pole suspended from the ceiling.
Use a white wall as a backdrop, and create your own background in photoshop using Render Clouds and Hue adjustment.
