Japan's currency is collapsing, which is bad news for US homebuyers because it could push mortgage rates much higher.

• Japan spent a record 11.3 trillion yen in April and May trying to stop its currency from falling.
• Japan has been a huge buyer of US government bonds, which helps keep US interest rates low.
• If Japan is forced to sell those bonds to defend the yen, US mortgage rates will jump sharply.
• Mortgage rates got a small break during the Iran ceasefire talks, but the relief is temporary.
• Higher gas and oil costs are already adding roughly $500 a month to the average US family's bills.

Outlook: Expect mortgage rates to push higher in coming months as Japan's currency problems force more bond selling, with double-digit rates possible if inflation stays sticky.