The way they do it in the US (at least Florida) is that they're paying you for your "time", not the plasma itself. So ::officially:: they're not buying it, but really they are.

I thought it was a typo for "task". Not a business person though, so I'm not sure about the lingo.

Have you tried any of the online sites? I've had nothing but terrible experiences.... Tutor.com and Wyzant especially, but also a local one. Do you advertise on CL?