I believe jt87 mentioned that. The cheapest I had was for a shade sail installed by a local guy with relevant council docs for 2k or thereabouts. I haven't Pursued anything as yet but will let you know if I do.
I have been looking at this as well in Qld, my property manager says we loose 50% of applicants because we don't have one. I thought of a shade sail that would be even cheaper but not sure about the look!