In Canada, renting a car when you're under 25 years old is pretty annoying. It's usually an extra $25 a day and that's what turned me off to renting. Some rental companies won't even let you get a car if you're under 25. It's actually a function of age, so I'm currently 24 and in theory, it should be cheaper now.. so let's do some blanket math to entertain your idea.

- I drive my car only on weekends, so Friday - Sunday

- It tends to break down every 3 months, at around $1000 a repair each time(BMWs have expensive repairs.) That's $4000 a year

- Insurance is about $1750 for a year

- Looking at rates at www.enterprise.com for my city, it's about $100 CAD for a rental car for 3 days (pick up at 7:00AM Friday and drop off at 4:00PM on Sunday.)

- $100 CAD * 4 is about $400 a month for a rental

- $4000 (repairs) + $1750 (insurance) + $120 (stickers) is about $489 for owning

It looks like using rental cars on weekends is not a great investment still and that makes me sad. I only save $89 a month and have to deal with picking up and dropping off the car and also not using it through the week. $1068 in yearly savings is not worth it!

Note: Gas is not included because I have to pay for gas for both cars, I guess it might be a little cheaper for the rental cars since they tend to be gas efficient, but I still don't think it's huge savings.