We have taken in a clutch of rats from a lady whos son had bought a male rat to keep his other male rat company.  a few months later 32 Rats plus three very probably pregnant females. 

The moral of this story is please get osmeone who knows to double check the sex of the animal dont take the sellers word for it.  they are cute very friendly rats who will all make lovely pets,  if you are interested in adopting rats please get in touch soon as the three females could bring the numbers to 60 plus.