Mag is just for surface indications,in laymans terms just a hair better than the eye. if you got your stuff together you could test in a few months. It does cost a little but it'll pay you back. inspectors usually make $3-5 more per hour than welders and in some cases more than that. It's also a little less strenious work.
A few things to think about as an inspector (CWI or not)
1. A good inspector does get dirty.
2. Not everybody hates the inspector, you have to earn the respect of the peoples work you are inspecting, in other words know your job, and report your findings in a professional manner (with out being a A**)and you will not be hated, you will become a respected, and well used source of knowledge.
3. Don't fool yourself the CWI is a pretty tough exam, remember you are not exspected to memeorize the code book cover to cover, however you must be able to find the answers in the code book in a timely manner.
4. Being a good inspector is just as much a fram of mind as it is a base of knowledge.