I am a Property Manager in Calgary.
In Alberta, you are required to be licensed by the Real Estate Council of Alberta to "trade in property management" i.e. manage rentals, show properties, collect rent etc...
Now there are several companies doing this without a license which is illegal and exposes their owner clients to alot of liability... What happens if they show the unit and accidentally leave a door open and someone breaks in? Are they even insured?
You can actually verify license status in Alberta by visiting
https://www.reca.ca/online/aspx/pubinquiry.aspx
I suspect in Ontario there are similar rules for licensing and you should be able to easily verify license status.
Additionally ask for references. My existing clients regularly give me references for new prospective clients, if your property manager does a good job then they should be able to give you mulitiple references.
For fee structure expect to pay 8-12% for a single family home, condo, townhouse. I have seen up to 15%, but that seems pretty high to me. We charge on average 10%.
Also there will be a separate leasing fee for vacancy turnovers. Anywhere from $350 to one's months rent, depending on the company.
Hope this helps. Good luck.