You must give more information.
First of all, since you are new here and completely unknown, using the escrow service is mandatory. Certainly, my advice is that no one agrees to your service without escrow.
You should emphasize what a small percentage it is. For someone, anything over 1% is a lot, while for someone else, 5% is a small amount. Be more precise.
It is also necessary to define the conditions and methods of determining whether some coins are clean or not.

This is not as simple as you make it out to be.