Rats need special housing, they cannot be maintained in the small quarters that mice or hamsters thrive in. Although plastic "starter" cages may be attractively priced, young rats quickly outgrow them. Rat cages need to be made of wire with small openings rather than larger openings. A cage designed for ferrets or other larger animals may work for fully grown male rats, but a small female could easily escape. Some special cages are designed to fit over the top of aquariums, these can work well. An aquarium on its own may be useful as a "hospital" tank or as housing for a female about to deliver babies, but generally tanks don't provide enough opportunities for climbing and exercise that cages do.
We will be creating some custom cages for our rats in the next few months, if you would be interested in checking these out or purchasing one let us know. They will be approximately 6 feet tall, 1.5 feet deep, and 3 feet wide. They will include at least 5 levels, and "half-levels" can be included also. I am personally not a very big fan of cage calculators, I think they have several flaws inherent in their design. However, according to more accurate cage calculators these cages will hold between 12 and 15 rats comfortably. I will have prices available as soon as I have priced the materials out myself.
There are several varieties of bedding for rats too. While pine and cedar shavings smell good and are cheap, they are also a danger to your pet rat. These litters tend to be dusty and contain harmful oils that can hurt your rat. Personally, I use carefresh, although there are other similar beddings available. A paper based cat litter will work well, and so will corn cob based litter.
I would also like to add that I absolutely love baking soda. I use it to absorb odors, especially because we have a small house. No one wants to smell rats the second they walk in my front door. Another one of my "dirty little secrets" is that I use newspaper as the base in my cages. I don't use the heavily printed pages, and this goes under the litter in my cages. I sprinkle baking soda on the base of the cage, then cover it with newspaper, then put the litter on top of that. This makes clean up quick and easy.
Rats can be litter trained if you put a litter box in a corner of their cage. Remove the litter from the rest of their cage, covering the surface with newspaper or cloth and place some dirty litter with the clean litter in the litterbox. If you maintain this routine for a few weeks, the rats will begin using the litterbox almost exclusively. While you will still need to clean the cage, this can cut down on cleaning time and work.
Your rats also need free time outside of their cage. This is a chance for them to interact with you, and also to explore. You can set up a special table just for your rats, or you can put a sheet over an every day table or your bed. You will learn why the sheet is important after around ten minutes of free time. Even the best litter trained rat still likes to mark, and when you are done with free time it is easy to throw the play time sheet in the wash.
Make sure your rats have plenty of toys and fun things in their cages. Some rats like to sleep in hammocks while others like to chew on their hammocks. Climbing ropes in the cages are also fun for your rats. Include lots of hidey holes and nesting boxes for them to sleep in and play in. When I have an especially dominant alpha in a cage, I always make sure to have one more empty box or igloo than there are rats. You don't need to spend a ton of money on these toys, although if you wanted to you could quite easily.
Store bought toys and items can include those for rats, as well as those for parrots. Lots of parrot toys are made to be chewed up and climbed on. You can also use things you have around the house. Empty cereal boxes can be widened to fit a chubby male, or left the way they come for a lithe female. You can use old worn out clothing that doesn't fit to make climbing ropes or hammocks. Have fun with it, and before long you will find yourself looking at things you are about to throw out and saying "I wonder if my rat would like this?"
More information will be added as time allows.