By the 10k do you mean the grant? I'm not that up to speed with WA laws, but purchasing an IP may implications on your ability to access grants/duty concessions.
In Cbr, if you own an IP, you wont get the duty concession.
If you haven't already, I'd speak to my conveyancer/local OSR to confirm that you can do this.
Cheers,
Redom
Same in WA - if you buy IP first, no FHOG for you. If you want to take advantage of grants though, you could potentially buy the cheap house first and get the $3000k rather than $10k though, live in it for 6 months then convert to IP and buy PPOR. If you buy sub $400k there are other concessions too to help with purchasing costs.