Depends on what his/her skills are. I have a bad back and have taught at the local community college. I can also program, but you need degrees and certification for that. And experience. Programming pays but can be frustrating at times.

There's management which is high paying but you need to have degrees and experience and be able to manage people. Tax accounting is also an option, again you need certification and education. Counseling can pay ... same old song, though "degrees and certificaton".

Look over the "help wanted" ads on various sites and see what jobs are open that your friend can do.