[Question] Evidence on correlation between making less than parents and welfare/​happiness?

Edit: Big thanks to all those who have re­sponded to this. I have up­dated my views to be far less con­fi­dent in my pre­vi­ous as­sump­tions :)

I am in a friendly de­bate with a friend about the im­por­tance of find­ing a job that pays a lot of money. I am pretty con­vinced by the ev­i­dence that af­ter a cer­tain in­come ad­di­tional in­creases barely in­crease hap­piness. My friend is skep­ti­cal about how these var­i­ous stud­ies as­sign causal­ity and in par­tic­u­lar thinks that they don’t pay enough at­ten­tion to mo­bil­ity. He claims that mak­ing less than his par­ents would be detri­men­tal to his welfare and hap­piness since he is ac­cus­tomed to that life style. My in­tu­ition says that he would just ha­bit­u­ate to a less ex­pen­sive lifestyle but he doesn’t think this is true. Does any­one know if there has been re­search on this? He has ex­pressed that he would love to be con­vinced that he didn’t need a high pay­ing job to be happy. :)