Now there is one loophole with this.
You can have owned an investment property that you never lived in and still get the fhog when you purchase your first principle place of residency. So if you want to buy an investment property first you can, however, you still can't get the fhog for it because its an investment. Basically you will only ever get the fhog once for both of you.
Most people get this confused, but you can, I went through this for a friend a while ago.