Renting a car in toronto. I will stay in Toronto for 3 months. Does anyone know the rent in Monthly bais?

if you are in the city, use public transport and rent as needed, especially for weekends.
for really short trips and only occasionally, use one of these:
http://www.autoshare.com/
http://www.zipcar.com/

you might also try these folks for longer term: http://rentawreck.ca/

or try these:
http://www.torontoautorentals.com/cars.aspx

If you're going to spend most of the time downtown or in the metropolitan area, you don't need a car. It's very hard to get around the city with your own vehicle. I'd suggest you use public transit and cabs. If you need to get out of the city occasionally, rent a car then.

For three months, it is almost certainly cheaper to buy a cheap car, and resell it at the end of your trip, or just drive home (if you live in the Americas).