Me and my sister recently bought a pet rat each. I named mine Samantha, and Sarah named hers Lilly. We have just finished building them a new cage out of two run-of-the-mill pet store cages. It involved removing the top of one, the bottom of another, and cable tie-ing them together.
For two rats, I think the cage is PLENTY big enough!
Jack also bought Rats, so if ours, (or his), need somewhere to stay, we have it covered.
Mum absolutely adores these two, and can often be found either; With the Rats, making something for the Rats, or on the best Rat site on the net (The Dapper Rat). Just today she made them a sleeping bag from a fleece blanket, and an old towel. Thanks Mum :-)