As Neil said, you might be on your own.
But with most big developments a QS company will have been in the picture - the banks often want them involved. If that is the case, that QS company will have the information needed to produce a Depreciation Schedule. They will often offer them at a reduced fee because they have all the costs. This is the case if you buy, for example, a Meriton property.
You need to act on this before you settle and tell the vendor that as you are an investor you are expecting a full Depreciation Schedule specific to your lot. Do it settlement, because once you've got the keys you really will be on your own.
Scott