Hi again Karen
If your parents would be able to meet the Balance of Family Test, then they could consider a Parent or Contributory Parent visa. Please see here:
http://www.immi.gov.au/migrants/fami...nt-outside.htm
If not, the next thing to consider would be whether they could afford an Investor Retirement visa instead. Please see here:
http://www.immi.gov.au/visitors/spec.../405/index.htm
Those are the only two options which would enable them to come and go from Australia as & when they choose and to stay for as long as they like during each year.
Depending on the visa, if they want to buy land in Australia and they do not have Permanent Residence there, then I think your parents would probably need the consent of the FIRB if they want to biuy a house there. Please see here:
http://www.firb.gov.au/content/default.asp
I have heard (but have no direct knowledge of this) that non-residents can buy blocks of land and have new houses built, but that they cannot normally buy alreadu-built houses. I don't know why this is, but it is what everyone seems to believe.
There are various types of tourist visa for Oz. Please see here:
http://www.immi.gov.au/visitors/tourist/index.htm
However, DIAC is becoming very, very strict about the notion that people cannot use tourist visas as a means of "living" in Australia even temporarily unless they have a visa that specifically grants either Permanent or Temporary Residence. Tourist visas are entirely at the discretion of the Department as to whether to grant one or not, and they do not grant any right of "residence" in Australia.
They used to be willing to turn a blind eye to parents like my mother, who were virtually living in Oz year-round via the subclass 676 tourist visa and its predecessors. However, the Senator Vanstone clamped down on this whilst she was the Minister of Immi. The older the parent, the more difficult it now is. Also, they are not happy about the notion of six months in Oz and six months elsewhere as a long term routine, even.
Have a look at the stuff and then come back to me if I can help further, I suggest.
Cheers
Gill