You can go by websites. But you need to include a due diligence clause in your purchase offer. Then send in a building and pest inspector, also get some independent rental appraisals.
Thanks for the link u sent , I checked it out. Unfortunately the Mac version is really old and doesnt work on new Macs.
I did some searching an found one called Property Investment Calculator at http://www.propertyinvestmentsoftware.com.au/ which I am now using. They do Mac and PC.
So far so...