Cages
A canary must be kept in a cage at a very minimum one cubic foot (1'x 1'x 1') and have at least two perches. Canaries like to hop from perch to perch and some will say that having only one perch is inhumane. A cage of the dimensions above is the absolute minimum as required by the Colorado Department of Agriculture (Breeder Regulation). I believe that a canary should not be kept in this small of a cage on a permanent basis. Small cages are OK for separating fighting pairs or to separate a bird to try to determine its gender. Males will usually start singing right away if you give them their own cage. A canary should really have a cage big enough to allow it to fly a short distance. A general rule of thumb - the bigger the cage the better. Most people will recommend that you buy the biggest cage you can afford.

Flights
Flights are bigger than cages, usually big enough to keep many canaries and often times they are big enough to actually walk into. I have a large flight made of 1" x 1" pine furring strips and 1/8" thick plywood. The flight was built around a sheet of plywood. The floor and top are uncut plywood 8 feet x 4 feet. It is seven feet high (I had to cut the height to fit it into my garage!). I built it myself and the materials only cost about $300. The advantage to using a big flight is that you can house a bunch of canaries and the labor is greatly reduced. You can use a common water bottle and food tray eliminating all your little food dishes, cups and bottles that you would otherwise have in smaller cages. You can also give community baths, medicate all your birds at once (medicate the water) and feed treats to all birds at once. It also seems that the food goes further since the ones that eat less leave more for the rest. There are disadvantages also. It is much more difficult to catch the birds. If you go after them with a net there is a possibility that you will hit the bird with the rim of the net and kill it (which I have done before). Here is a trick on how to catch birds in the flight - turn out all the lights in the room (at night if you have windows) and use a pen light with your thumb over the end. Let out just enough light to barely see the bird. Your eyes are much more sensitive than a canaries and can see better in dim light. You can use this to your advantage. If they fly in the dark you should remove your thumb from the end of the pen light completely and let them have more light so they can land (otherwise they will run into the walls). Another disadvantage is that if you don't have enough perches in the flight the birds can run into the walls and kill themselves. I lost several birds this way. They can't really see the walls if there is nothing to land on, kind of like a bird running into a window. Make sure you have plenty of perches and they are arranged so they don't poop on other birds or on other perches (or in food or water dishes). I would highly recommend large flights for serious breeders.