trust me, if they're living together and have been for about a week, expect some babies.

Rats do make excellent pets- Terra (my first rat) was much like a dog.
If you're really interested in them as pets, you can train them to use the toilet in one corner of their enclosure (simply spot check the tank and put all fecal matter into a small shallow tuboware container with a different substrate from that you use for the rest of the pen. they should eventually figure out where the fecies go.)
(even if not pet wise- potty trained rats are a godsend on cleanup ^^d.)

Just a note, right after your female has her pups, i would suggest removing the male if you dont want another litter of pups asap. if you want to keep them as pets and are concerned about their health, wait until the pups are done welping before putting her back with the male. if these are more of a breeding venture then dont worry about the above.
just making note. (since you only have one bp, by the time your first litter are growing a bit of space inbetween litters shouldnt cause you to have to skip a feeding)