It's almost impossible to accurately estimate how much in transfer funds is available to the club as we've no idea whether the Board wishes the debt position to increase, stay the same or reduce. I'm guessing they'll want to reduce the debt position (ie the size of this years Vibrac loan should be lower than last years @£20.9 million)
So it's a movable feast I am afraid. At the operating level the club is now generating cash, ie our income is greater than our expenditure which is obviously a good thing.
@Visitor22 mentioned earlier that our profits last year equaled the profit on Fellaini's transfer. Whilst that is true our profit was reduced by the amortisation of the player contracts which of course is a non cash item. So last year (2013-14) the business generated around £18 million in cash. I'd expect a slightly higher figure this year (before player trading) as we received higher prize money for our 5th finish, we participated in Europe and our attendances were higher.
If I was to offer a guess I'd say a maximum of £20 million net is available this window - but that's a guess.