For litter training, I got two seperate litter boxes (you can get less, I just figured it would be easier for them to learn with two). Then I covered the floor of my cage in fleece, and put the bedding that they're used to in the litter box (Carefresh). They won't get the hang of it right away- which means that you'll have to pick up poop and put it in their litter box. And if you see someone using the litterbox, be sure to praise them. When they learn how to use the litterbox, you can take out any extra litterboxes that you had in your cage one by one.
Why in four months? When you do get a new rat you'll have to keep them apart (as far apart as possible) for three weeks... search about quarantine (QT) and introductions. Remember to be patient when introducing new rats to each other.
well im about 14 and this dumb pets mart lady told us that there okay alone and actually went as far as to tell me that theydont like having other rats around so even if i ask my mom shell think i just want to get another one and not like this one so until i get some money witch i spent on new skateboard i might be abel to get one for christmas
Before you try too hard potty training, let your rat (hopefully soon to be rats!) figure out where they want to go to the bathroom first. Then you pick that spot to put the litter pan in.
See if explaining to your mother that the petstore lady didn't know what she was talking about helps. Show her websites, like this one, that say that rats need friends. A lot of people, even those that work at the petstore, think that rats are basically hamsters with funny looking tails, and some hamsters should be kept solo. But that's not correct for rats at all- ask her if she thinks cats and dogs should be treated exactly the same, and explain that rats need the right kind of care, too. But be nice about it, of course.
It's never too late to give your rat a friend, just make sure you go through the proper quarentine and introduction steps. But if at all possible you shouldn't wait for four months, that's a long time for your rat to be alone! Every ten days is a year to rats, so that's like making your rat wait more than 11 years for a friend! Yikes!