Haha, i had the same problem. Too many mice / hamsters to take care of, too many GM's that i couldn't afford.
The only way to offload them is if the CF [Cromimi Federation] take them away - but that way you have to mis treat them which is kinda sad.
Other than that, i guess you could send them on a career?
Ŷőũŗ Łŏvę Ĩş Mŷ Ťŭŕŋįņĝ Påģē