Data – What, where how much

I am curious as to the data people look at before investing in a particular area.

For example, do you look at:
– Age of residents in the suburb
– Weekly income
– Number of renters to buyers
– Education level

Or only look at things like:
– Rental yeild
– Capital growth over x years

Any details about the sorts of data and where you get that data (freeis always best) would be greatly appreciated.

Thanks
Brett