You could probably hire a person with a piece of heavy equipment like a bucket loader for a half day to knock it down for you, and it might cost you $400 or so provided there wasn't too much rebar to deal with. If you want someone to do something about the rubble, that's a whole 'nother can of worms.
I have a 2 car 1 story detached garage that is made up of cement blocks. I understand I will not get an exact price but if someone had something simular demolished it would be nice to know what you've paid.
thank you