Life Span of Pet Rats: about 2-3 years.
Size: pet rats reach a body length of about 9-11 inches and their tails add another 7-9 inches (males tend to be larger than females)
Social Nature of Pet Rats: rats are very social so are best kept in same-sex pairs or groups. Pairs/groups of either females or males will work, especially if raised together from a young age.
Habits Of Pet Rats: rats are technically nocturnal (active at night) although many pet rats adapt their schedules to that of their owners, waking to play and socialize when people are around during the day. They are playful, curious, and generally easy to tame especially if handled from a young age. They do tend to urine mark when wandering about, but this is usually such a small amount that it is not offensive.
Other Considerations: a large multilevel cage is a good idea for rats, which love to climb and explore and play.
More on the Care of a Pet Rats
Pet Rat Fun