Welcome on board and congratulations on working towards your dream.
In answer to your question I have to qualify what I'm about to say by pointing out this is one of those times you need to get proper professional advice and this is general information only. Depreciation is a fiddly area and there are a whole bunch of possible outcomes depending on your profile and what you're buying.
Also, I am assuming you are talking about depreciating the fit-out for tax purposes rather than accounting purposes.
Fit-out costs can comprise a whole bunch of things ranging from walls and other fixed items, to large items of equipment, furniture and smaller items of equipment.
For all removable items, furniture and equipment you are able to deduct these outright (so the equivalent of an expense on your P&L) for tax where they cost < $6,500 each and you are a small business (turnover < $2 million). For items above that, these are thrown into whats called a general pool and depreciated at 15% in year 1 and 30% of the written down value each year thereafter. Some items can't go in the pool (like software, assets that are leased etc) and have to be depreciated under the normal rules.
For items that are considered 'capital works', generally standard walls, floors, doors etc. that don't perform a particular function in your business, these are deductible at 2.5% straight line over 40 years.
More information here http://www.ato.gov.au/businesses/con...=16#P452_27220
Generally people let their accountant worry about the depreciation as they have specialist software, plus the knowledge, to work it out reasonably quickly.
Hope this helps!