I personally know the owner of 3 Tim Horton's locations in Peterborough. As he puts it "It is disgusting how much money you can make selling coffee.".
The trick to making a ton of money is like anything else, the more you risk the better your pay out if it works out. He bought the first location early on in the 90s. Back then the brand wasn't what it is today. He was taking a big risk and he continued to take big risks by buying 2 more locations over the next 5 or 6 years. But now the guy is one of the wealthiest guys I know.
I think if you wanted to buy a franchise you'd have to be a pretty savvy business man. Anybody can see that buying a Tim Hortons is a good idea. But it costs a whack load of money and a lot (if not most) of the good locations are spoken for.. So your chances of striking it rich are slim.
In my opinion you'd be far wiser to buy an "up and coming" franchise (like Burrito Boyz or Ali Baba's) and hope that they work out in the end...