Should I build a duplex in Mount Isa

Hi all,
I have just purchased a property in Mount Isa suitable for a duplex at the rear of property. The completely renovated house needs nothing spent on it and has just been leased for 12 months at $300.00 a week, purchased for $165,000.00 privately.

I can subdivide keeping the house on one block and building on the other, total land area is just over 1000 sqm. I am currently getting plans drawn for duplex which will be 2 bedrooms each. I have been quoted the going rate is about $1200.00 a sqm to build by a couple of builders in the town. I am going to build in split face block with corrugated roof.I have not got any builders prices yet,only verbal rough rate, but would expect anywhere from $280,000 – $350,000 to build, depending on whether patio’s are included in sqm costs, the the total area of duplex is 288sqm including front and rear patio. Brand new 2 bedrooms would rent for $250.00 a week in the current market.

This is my first development as such, but i have bought and sold investment properties a couple of times successfully and would appreciate any thoughts on whether this project sounds a goer?

Here is one of my questions to other forum readers! Has anyone recently built in Mount Isa this type of development, any builders to recommend, any suggestions to save on costs?

Thanks
Don

djr