to be paid do you need a class one or class two medical?
A PPL requiures a Class 2 and a CPL a Class one, so if you instruct using PPL privileges you only need a Class 2 medical. The privilege to be paid is part of the EASa privileges of the PPL.
You are probably thinking back to the days of the CAA ratings pre 1999 when a Class 2 was required to instruct, but a PPL only needed a Class 3.