That's strange. I made an offer for a bank repo just a few weeks ago and was told there was nothing to pay for a while. In fact, they said it would likely take the bank several months to process the sale. That was one of the things that made me pull out of the deal in the end - I wanted to get on with it!
Are you sure it's the bank stipulating this, and not the estate agent? When the bank has been hanging onto the property for (probably) several years, I would have thought a little flexibility would have been possible, although the agent may be in a hell of a hurry. I imagine there's no mortgage involved as that would be highly unlikely to go through in a month. What then? It all sounds rather odd, IMHO. Have you consulted a lawyer? A simple yes/no answer to your question may well come free, particularly if you're likely to be future clients.