For Corporate Finance, it is totally useless. If you get a job which requires Module 4, the coy will pay for it and you have to go for it. There is no point doing it outside yourself. Having passed module 4 would not give you legs up in any way. It is really easy to pass. Up to you if you wanna take, but my advice is for you to save that money up. Do CFA or CPA if you use extra papers as a route to Corporate Finance.