Friend asked me to be safety pilot so he can shoot approaches in his C182  

"A requirement not mentioned in §91.109(c) is medical certification. For that, we look at the medical requirements in §61.23. As the Chief Counsel said more than 40 years ago in the 1977 Josselyn Letter, “a pilot who acts as a safety pilot during simulated instrument flight … is a required pilot flight crewmember… [T]he [safety] pilot would have to have an appropriate current medical certificate.” In 2020, the “appropriate medical certificate for exercising private pilot privileges is “at least a thirdclass medical certificate…except when operating under §61.113(i)” (BasicMed).