I know some people just never have seen this word before, but commission means paid work. "Free commission" is an oxymoron because of this!
I received a note the other day,
"I was just wondering if you'd be willing to do a commission of a Pokemon team, but if you are I was also wondering if you would be asking to be paid for such a commission."
Please please please don't be like this person; learn what words mean before you use them in a sentence!