Hello Lotana,
I did a lengthy reply to you which got deleted after I hit the preview reply button.
I advise visa applicants on this from time to time.
All temporary visa holders need FIRB approval to buy "second hand dwellings". Until this person obtains the PR visa they will need to apply for approval. The link to FIRB is: -
http://www.firb.gov.au/aboutus/about_us.htm
Usually approval is given if the person holds a temporary residence visa valid for more than 12 months if they intend to use the dwelling as their PPOR and undertake to sell when they leave Aust.
There is also the exemption for some FIRB pre-approved developments (where no more than 50% of dwellings in development are sold to foreigners).
Don't confuse residence for immigration purposes with residence for tax purposes (different animals).
You could however include these facts in a submission to the FIRB explaining the applicant's time in the country, tax status, intentions on staying and likliehood of being granted permanent residence. If they are an applicant for the aged parents visa and likely to be in the queue on a bridging visa for many years this could also be explained in the FIRB application.
Hope this helps.
Ajax