Effects of new housing estate on existing prices?

hi all,

I am thinking of investing in a mining town in CQ that is returning around 7-8%. Vacancy rates seem to be low, however there is a new land subdivision of about 50 blocks that has just been sold and I am assuming houses will start to built in the next 6 months.

Will this negatively impact on current housing prices and rents, or do you think will have a positive effect on current house prices. There is a new mine that is going to be opened within the next 5 yrs.

Any predictions would be useful.

thanks