The IM is not required , but is one of the recommended training aids for the DM candidate (of course it is, it's more money changing hands), I have always found it helpful if the DM candidate has a copy as it has the guidelines for the DM led courses in it and the student can look back over the DM section when revising.
In England the IM retails from PADI at about $170. Try ebay.
In England the IM retails from PADI at about $170. Try ebay.