In this business we work on commission, are you okay with this?

"Absolutely! I am motivated and driven by my own performance. Commission compensation lets me control my own income, which is something I enjoy very much."

The only answer to this is yes or no which if you give a negative response might go against you so try to back it up by saying that if you were only taking the job on a commission basis then it would be an incentive to work extra hard to get the best sales as your salary would reflect this. Turn a negative into a positive!