Home, sweet home. 
Remember, rats spend a great deal of time in their cage when you are not playing with them (unless they are free roaming rats), so make sure you get them the biggest pad you can afford, so don't think their hamster cage is good enough for them. Especially if you get couple of male rats, they will grow and they will need a bigger cage. And good cages are not cheap at all. You get to decorate the cage for them with platforms (not too high though!) ladders, climbing ropes, hammocks, nesting box, water bottle, etc. Place small cardboard boxes that rats can  chew and hide inside. Their essential furnishing is gnawing sticks. It's a block of hard wood that you can buy in pet shops, to keep those ever growing teeth trimmed! 

Running wheel is something you should watch out for. I bought a large wire frame wheel when I was still a novice Rat-master only to learn that my rats hated it. The looks, the sounds it makes, they were petrified when they saw it. I also learned that rats tend to have injuries and accidents because of it. But there is a very clever and safer version of a wheel called Wodent Wheel, which has been recommended by many other Rat-masters that I know. The Wodent web site has some wonderful photos of rodents in action too! 

Wire frame cages are good because they are easier to wash, but you should be careful when you buy a cage with wire floor. My rat had her poor little foot stuck between the cage wires several times. Also it is know to cause a medical condition called "bumble feet". You should get some wood or a hard plastic sheets to cover the floor.

The rat cage should be kept in a quiet, dark and draft proof place in your home under a stable temperature. Never under a direct sun light or a garden shed. Too much humidity causes "ring tail" and warm places will make the rats to overheat and dehydrate. Of course if you have other pets make sure that rats are kept safely away from them.