Mailbox Question for a SFH that is being used as a Duplex

[Sai Kopacek]

Good Morning! 

My wife and I are looking at purchasing this awesome single family home in Martinez, CA that is currently set-up as a duplex. Both units are about 1,700 sq. ft. w/nice kitchens, bath rooms, and laundry - each with separate entrances. 

My question - Is it possible to just put a dual mail box in place of the single mail box? With Unit A and B on each mailbox door. I am going to start calling the city to find out more, and see what needs to be done. I just haven't dealt with this in the past and wanted to see if anyone else has had this issue?

Cheers,

Sai