When you are expecting some new baby rats, you will need a few items to be ready for your babies. First off, you will need a cage. I always suggest a wire cage. Some example of a few nice cages are a FN cage, they are on the more expiencive side but are good for some one who is planning on having more then two to three babies. There are some cheaper alternatives such as these cages from Pet Smart. There is always the option of the DIY cages, I like this option because you have so many different ways you can set up your perfect cage for your babies.
Here are some Great Links for some DIY cages thanks to RatFanClub.0rg
I do not suggest tanks or glass cages. They have little to no air flow and can cause more problems to your babies then you will want. The ONLY time I use tanks, if for a birthing mother. So when the babies are born they won't be able to fall through shelves, or bars and can be safe for a couple of day.