Am I allowed to buy residential property in Ontario on a work or study permit if I'm not a citizen?

It depends on your specific situation, and this is not a question to answer from a general rule of thumb. The federal Prohibition on the Purchase of Residential Property by Non-Canadians Act restricts non-Canadians from buying most residential property in Canada, including in Ontario, but the rules made under that Act carve out exemptions for certain temporary residents, which can include some work permit holders and international students who meet specific conditions set out in the regulations - things like how long you have been in Canada and the nature of your work or studies.

Because those conditions are detailed, technical, and the kind of thing that gets refined over time, you should not assume you are automatically exempt, or automatically barred, just because you hold a work or study permit. Whether a particular purchase is permitted turns on your exact immigration history and status measured against the current regulatory criteria, not simply the type of permit you hold.

Before signing anything, confirm your specific eligibility against the current federal rules with your lawyer, since buying in violation of the ban carries serious consequences covered in a related question.