If it's two crew you would need a type rating. If £15k includes that then I would go for it.
If not it sounds a bit weird, I would give it a wide berth. You would need FAA licences which would add to the cost. And if it's single crew on the AOC I'm not sure how those hours will look back here. The captain can't let you fly it if your not type rated. Even if he did you can't log it.