My sister had her landed immigrant status in 2002 (has her SIN and health cards). She did not stay in Canada, and moved back to Hong Kong. She now wishes to live permanently in Canada, and purchase a condo in Toronto. What must she do regarding notification / application?
She can buy property here pretty much no matter what. Her status only affects how she will finance the property and what down payment is required (if she is getting a mortgage).
I'm not familiar with what "landed immigrant" status means, but if she is a Permanent Resident, then she can buy a property in Canada. There are institutions that'll give her a mortgage with as little as 5% down (if she is working, but no credit history) or 35% down (not working, no credit history). It really depends on her case.
If she doesn't have status in Canada of a PR, then she will be considered a foreign buyer. Minimum 20% down payment is required at most banks to give mortgage. On top of that she may be charged a 15% foreign buyer tax. But if she gets PR within 3-4 years, then she can apply to get that foreign buyer tax refunded. More details no that tax here:
https://www.fin.gov.on.ca/en/bulletins/nrst/
Good luck to your sister!