I recommend you invest your time in calling and is looking up the costs. It is best to get as accurate as possible even in the do diligence phase rather than settling for a rule of thumb. When you're looking at something This size you have to be even more diligent with the numbers. 

Costs will range from council the council and you will be surprised at how this can all add up. I know it's a lot of work but it's well worth it and it will help you guesstimate in the future as well.

I am currently getting $290 per week for my granny flat you might as well not call it a granny flat it is pretty much a self-contained unit. This is more attractive the renting a unit because I've sectioned off the backyard to give the tenants their own privacy. 

Also there is no stairs and the property is only been shared with one house and gives the tenants complete privacy. We live in the front house but were looking renovating that and renting that out as well that will go for $380 per week there is so much you can do when you think creatively.

I suggest Kimberly you think about your desired outcome and that you screen your tenants with the utmost diligence.

You just don't want anyone living in your backyard.

Also check out one of my articles about what can help you attract a tenant and where you should spend your money. http://realestatesevenhillsnews.com.au/2013/02/4-secrets-to-what-attracts-a-tenant-to-a-property/

I see many people com­ment­ing on for­ums say­ing “Sydney as a whole is way over­priced for what is selling” and "Sydney house prices are depressing…"

Where we all want to live, well most of us!

I can sym­path­ise that most people simply want the com­mute between work and home to be shorter, but these days we also want a great school for our kids and to be close to our family/friends. Our men­tal­ity has changed because we also expect to step out of our door and walk to bars, res­taur­ants and the train station.

This is a life­style factor and some of us have accep­ted to live in a shoe box or pay big bucks for some breath­ing space. This life­style factor has become such an ingrained way of think­ing. People are even start­ing to think noth­ing exists past Par­ra­matta, such as mobile phone cov­er­age inter­net and connections.

A good example of this is a com­ment in reply to city people com­plain­ing about Sydney house prices “It almost sounds like they have not moved from the city for dec­ades and still think that the city is the centre of the uni­verse and that noth­ing else exists.” He also added “Or is it that it is still the centre of the uni­verse for many people?”.

If you have a "10/20 years time" out look and you really want to make sure you lock in that capital gain. 

you can do this 2 ways;

1) Ad a higher or better use to the property/land (renovation/build)

2) Do your due diligence and focus on local Infrastructure

I break it down how Infrastructure leads to property growth in my article about Blacktown. 

You will probably want to go on RP data and look at Days On Market and double check that they have sold if not dork knock them or direct mail them! that should get you on the right track.

Try http://www.gumtree.com.au with the ad. you can specify the location.

It is so true, and mostly slow at getting contracts together and kill many sales! 

Happens every in real estate, it's hard to find a good one.

There has been issues in the past were people have taken phones of the security system and been robed after the home open.

Before you sort out all of the loan issues (which sound like you will not have a problem) you need to decide what sort of investor you wish to become?

Do you want to invest for Pos­it­ive Cash flow, Neg­at­ive cash flow, ren­ov­ate & sell, Sub­divide or develop. These strategies are very dif­fer­ent from each other and require a dif­fer­ent skills set.

Of course you can learn these skills sets but you first need to mas­ter one strategy before mov­ing onto some­thing different.

For more information check out this airticle 9 Steps To Successful PROPERTY INVESTING.

I can't see how you are finding it hard to find positive cash flow property?

I admit it is hard to find one with a 10% yield already built into it.

I find with Western suburbs of Sydney (Toongabbie/Blacktown) you need to find the value I.E. a half finished granny flat or one needing updated.

A quick renovation a boom instant cash flow!