My wife is in uk work permit visa . I'm also in uk on 5 year work permit visa . How can my wife change her visa statue from workpermit visa to uk dependent visa

My wife is working in UK and she holds a work permit. Kindly advice me about the procedure to get a dependent Visa,. like.. documents required,

What is the time required for the Dependent visa to process?

How much money is involved for the visa to be processed?