Toronto is a pricey city in terms of accommodation: be prepared to pay a higher amount of rent compared to what you'd pay in Stockholm. An average (private market) price of a room in a house varies from CAD$ 600-1100, depending on the area (proximity to St. George campus or Downtown etc.) and the type of housing. UofT housing is not that much cheaper, but the locations are quite convenient for students studying at St. George campus. Everything else apart from housing and public transport (especially monthly pass) is slightly cheaper in Toronto: eating out, buying groceries, alcohol and other goods is less expensive compared to Sweden.
As an exchange student, you will have to pay a CAD$200 fee for UHIP health insurance that every student at UofT is obliged to pay. This is mandatory even for KI students who get the Kammarkollegiet insurance, but is useful for general health issues. UHIP, however, does not include prescribing students with drugs.
How to keep the costs low? I'd recommend shopping in bigger grocery stores (such as No-Frills) and limiting the use of public transport, if possible. I find it very easy to walk or bike in Toronto and the streets are safe even during nightime. Some grocery stores (like Metro and BulkBarn) have a 10% student discount on a given weekday, which contributes to economical living.
Labs might be able to compensate for the work which, however requires to apply for a study&work permit from the Canadian Government. If the stay in Canada is under 6 months and you won't receive a salary or a stipend, there is no need to apply for a study permit. It, however, makes some things easier, like opening a bank account or applying for a credit card, for example.