i had a pet rat about 15 years ago , i had 2 level bar cage that was big enough for a guinee pig it wasnt that expensive to buy , i accidently put his cage to close to my curtains one night and he made a lovely bed out of them , ive learnt that getting a pet rat tame is very important as if they try and run its extremely hard to catch them .
i only had 1 so im not sure on how 2 should be kept , i do know that females are very territorial and fighting can occur .