In addition to Rockstar's info above,
I had a quick lok at rea.com.au to see what's available and selling and not many town houses for sale there anyway.
Double storey will also allow more open space for a small garden, courtyard and outdoor entertaining space.
Take a drive around and see what type of developments are in the neighbourhood. Also consider the demographiocs of the area/suburb. If they are mainly elderly retiree's then they may not wish to go up and down stairs.
Have you considered doing the development yourself?
Have you gotten reasonable indication from a town planner or council that you can do the subdivision and achieve three sites?
Is it a corner? Will they all have street frontage or be in tandem down the length of the block?
Perhaps seek info from a local town planner and guage what they feel the market wants there?
Sorry for all the questions, however the answers may help you attain more info to make your decision.