I heard there are some small rental companies owned by Chinese, they can even rent a car to a G1 holder. If you want to try, buy a Xing Tao Daily and find in these ads.
And, the price I tell you doesn' t include insurance.
Usually, the rental price is a bit expensive in weekdays. For weekends, they usually have some kind of promotion or discount if you rent it for the whole weekends.
National has a lot of rental stations in Toronto, you can rent a car from one station, and return it to another station. Within the same city, there will be no ONE-WAY charge for that. I always rent from Union Station, and return it back to Yonge & Bloor. At least these two stations are open in weekends.
Btw, no matter you have a job or not, deposit some money to get a credit card. It will help you to establish your credit record (history), which is one of the most important stuff here.