Sounds to me like the loan to value ratio of his portfolio has now exceeded the bank limit and they are asking for more equity to restore ratio. Refinancing will not solve problem as banks hate you leaving and will make it hard as well as other banks are now cautious. Your friend has realised too late that he does not have as much equity as he thought. Go to the bank and get them to provide a letter stating they will not give him finance, and cancel sale. If he did not make the offer subject to finance then he is a fool and in big trouble.
