The differences really turn on the use of the indicative and subjunctive cases in English. The indicative is used to describe the reality of how things really are, or were. The subjunctive is the unreal, or wishful way of saying something indicating that what is happening is not the real state of affairs. . 1) ''I wish I would have a job!'' That means you want a job but don't have one. It's probably a bit colloquial to say it this way. 2) ''I wish I will have a job!'' Probably should be re-written as "I wish to have a job.....in (some time reference) 3) ''I wish I had a job!'' That's more like sentence 1, and it's in the subjunctive. It means you don't have a job but want one. 4) ''I wish to have a job!'' That's written in the indicative and sounds like you are expecting to have a job at some point, perhaps soon. 5) ''I wish I could have a job!'' That tells me you want to work but can't for some reason (lack of work availabilities, disability, etc).

I wish I will have a job is totally incorrect

There're many English Forum websites out there. Go to any one of them and you will find loads of explanations of grammar problems like the one you asked.