A well-paying job is a job that pays well, while a good-paying job is a good job that pays.
As a compound word, well-paying is obviously correct as there should be an adverb (well) to modify the participle (paying).
As good-paying is also used by more and more people in informal speech, it cannot be considered incorrect either, but it should be avoided.
- As long as I’ve got a well-paying job here, I’m not going to relocate.
- We need to get more well-paying clients to keep our business alive.
- President Barack Obama made a strong case during Tuesday night’s debate for how his administration would create “not just jobs,” but “good-paying jobs.” (Source)
A well-paid job is a job that is paid well, which means that you are paid well in the job:
- They offer quite many well-paid jobs at the new IT company.