My tailor is rich. Why your tailor it is not yet?
Sounds like grammatically incorrect to me, but putting in context and followed to the previous sentence, would it be correct to say this?
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"Why your tailor it is not yet." is not grammatically correct with or without the "it".
I believe what you want to say is "Why is your tailor not rich yet?" or more shortly, "Why isn't your tailor yet?" (in this case, we would not say "Why is not your tailor yet?" because then it becomes awkward).
The "it" is unnecessary in this question because it does not refer to anything in the context of the situation. All we care about is "your tailor", but we already name him explicitly in the question.