Pictures of rats to show your parents to convince them to get you a few! (Don't actually walk them outside because they might get sick)
Such misunderstood animals. So sad to look up "rat cages" and the only thing coming up being traps. Despite their reputation as pests, rats are intelligent, clean and loving animals if you let them, and actually considered the smartest out of all of their rodent counterparts. Did you know they can use their exceptional sense of smell to find landmines and unexploded ordnance for humanitarian demining? I'm gonna bet no.
Do not even think about getting just one. These animals can only thrive with company. It is necessary you get a pair of them at the very least, but three is ideal. If you want more, my all means, go ahead. The more the merrier. Just make sure you have enough space.
I wasn't joking about the space. They need big and tall cages with platforms to climb on. Minimum requirements for a couple of rats would be 40cm x 50cm x 60cm. But if you were a rat you probably wouldn't enjoy the minimum all that much. I recommend something bigger, for example a critter nation small animal cage. It is sort of pricey. I'm seeing some cat enclosures about this size that look like they could work with a few modifications, that go for half the price, although I cannot tell if they're dense enough. You don't want your rats escaping through the wiring. Better safe than sorry.