From my experience, there's three types of people involved in dive operation management/ownership:
1) The experienced, enthusiastic diver with no business acumen. They often fail.
2) The experienced business-person with no diving industry experience. They often fail.
3) Those with both business acumen and diving industry experience. They don't often fail.
Doing an 'IDC' does little to provide industry or operations experience. Your friend shouldn't kid themselves that it would. Knowing how to teach an OW course doesn't equate to the breadth of knowledge necessary to plan and control safe, high-quality, customer service operations on a long-term basis. Sales and marketing is a good (maybe critical) skill-set for a general manager, but you can only sell and market a quality product (the scuba community being quite discerning consumers).
Your friend might be able to sell sand to the Arabs. Can he create the sand though?
The industry is also quite unforgiving. It's not an arena in which to 'learn by your mistakes'. Liability and media make dive operator mistakes quite damaging. As does the customer's word-of-mouth. There are a lot of mistakes to be made in running a dive operation - the DM/IDC courses provide nothing in respect to avoiding them.
If the potential employer was making such a deal, it might be wise to assume they they themselves have little industry knowledge? If so, the blind can be leading the blind.
