Loan on residential 4-plex that is zoned commercial?

[Ori Skloot]

Need some advice on getting a loan.

I am in contract to purchase a residential 4-plex in Richmond, CA.   We are going to buy it for all-cash and then we want to immediately get a loan on it.

The property has been zoned commercial for decades. The zoning law for the area was changed so that the building would now need to be a duplex.  The building is grandfathered in so long as it hasn't been updated. However, the current owner converted the downstairs floor to 2 units making it a 4-plex, which is not conforming to the new zoning.

My question: As it stands (non-legal 4-plex with commercial zoning) will it be a problem to get conventional or portfolio financing on this property?  

Your feedback is much appreciated!

@Chris Mason care to chime in?