The way I understand it you have to be the care provider.
Meaning you and they both posses the signed sheet that came with the tamper resistant recommendation. It did with mine anyway. I also think you are supposed to only be charging to recoup your cost not profit. I think you can only have one registered patient at a time. I will look for the department of health link and post it back here in a few.
Not sure if you have read it or not.
Here this may help. http://apps.leg.wa.gov/RCW/default.aspx?cite=69.51A&full=true