Kim's Ark is wonderful... I was shocked to see anyone mention them here, hehe! I've done transport for them for a while (stopped this past year, however. I can't travel much right now and I have a rescue litter I've been trying to adopt out since November).
a few basics to rats:
they need to be kept in same sex pairs or groups.
A lot of commercial and readily available rat food is... well.. bad.. so research what you're feeding them. Many of us use mixes with high quality low protein dog food as a staple with added other things (cereals, soy nuts, fresh fruits and veggies, etc), others use harlan teklad lab blocks which you can get from Kim's Ark.
Wire cages should be no more than 1/2 inches wide spaced bars. a normal 1 inch by 1 inch wire spaced C&C cube cage may be OK for LARGE adult males, but females will squeeze through and young rats will be gone fast (at least they return to their cages, but I'd hate to think of one getting their heads stuck). Best cages we all recommend is Martin's
www.martinscages.com. If you want to know the dimensions, check here: (broken link removed)
remember that floor space is MORE important than height, though.
rats are awesome.. they make great pets and I've kept them for 11 years now.. the BIGGEST downside to them would be their very short life spans.. they live 2-3 years, and many unspayed females die from tumors (males as well but I've had more problems with getting female tumors removed than ever with males). Also they have a lot of respiratory problems... and the cheap 2 dollar rat will very quickly become the expensive 200 dollar rat when you add up those vet bills.. trust me there *smiles*
( I got 2 females from a petshop.. (this was years ago) they were kept in a tiny cage, and they banged the door of the cage shut each time they closed it which caused the rats to jump high in the air! I haven't been to the petshop in ages but they really are awful. Well we brought them home and they had a really big cage.. but they never became fully tame through being in this petshop and they were quite old when we bought them so I doubt they were ever handled at young age. We handled them often and gave them floortime - there would be a bite now and again, but they were getting tamer. In the end one of them (Autumn) died of Phneomonia (don't know if I spelt it right!) The other one (Kirby) was lonely without her sister. We got in touch with a lady with about 5 rats and she said she would house Kirby with them. I think she is/was happy with them. So I was quite unlucky with my rats. They never grew that fond of people 
