For several weeks Elon Musk has been joining the voices of Cassandra, who foresee a real estate bubble bursting. 

He regularly alerts that the situation in the sector is deteriorating. 

For now, it's commercial real estate that's holding the attention of doomsayers. And the reason is simple: Commercial real estate relies on the health of banks and their ability to finance projects. 

Since March, not all has been well in the financial system, and more particularly with regard to the U.S. regional banks, which finance the major real estate projects.