Where will your rats live?
Rats need room to roam. The minimum cage size two rats can comfortably share is about the size of a 20 gal. long aquarium. A cage with wire sides is preferable, so that the rats can sniff the breeze and interact with you. (Just look out for your fingers if you often feed treats through the wires!) Make sure the bottom of the cage is solid, since rats can get bumblefoot from walking on wire-bottomed cages. Powder-coated wire is the best -- rats can get zinc poisoning from chewing on uncoated galvanized wire. Several levels are far more fun, so the ideal cage would be a flat-bottomed, powder-coated wire cage with a level or two for climbing and exercise. Also, a cage that's very large is hard for a single person to clean, so you have to balance size with practicality.
Here are some sites with pictures so you can get an idea of what's out there:
Fern Cage Mfg.
The Ferret Store
Martin's Cages
Of course, you can always make or modify your own cage! Here are some examples of neat real-life rat homes:
bclee's Rat Cage
Handy's Rats
Bramble's Ratty Abode
And here's a really fancy one:
rat haus
Of course, your rats will think the ideal situation for them is to be free-range ratties. This means that you dedicate one or more rooms as their living quarters, but those rooms must be thoroughly rat-proofed! All wires, valuable furniture and anything else you don't want them to chew on must be out of reach. Plus, watch out for any holes or small cracks they can squeeze through - the last thing you need is a rat lost somewhere in your walls or ceilings! This is a workable arrangement if you have rats who are fairly well litter-trained and if you aren't too fussy about neatness. It is fun, but impractical if you have rats who don't get along or rats of different sexes.
Here's a good link on ratproofing from Squeak!:
http://www.chirpy.com/squeak/ratproof1.h...
What kind of bedding will you use?
Pine and cedar bedding are both hazardous for your rats' health. They contain phenols, which make them smell good, but can harm your rats' lungs and liver and can contribute to myco flare-ups. Please find an alternate bedding for your rats! Aspen is a good alternative, as is untreated recycled-paper kitty litter like Care-Fresh. You may want to experiment with other beddings such as rabbit pellets, corncob, etc. Just beware of chemical additives and research your choice thoroughly! Remember, your rats will be living in, nibbling on and breathing in the stuff. If you don't have access to bedding that is known to be safe, ask other rat owners in your area what they use and why. Also, do plan on cleaning out the cage every 4-5 days to prevent ammonia buildup, which can also damage rats' lungs.
