Duplex -> Single Family

[Michael Mason]

I'm looking at purchasing a property that's zoned for a duplex, but the seller appears to have converted it into single family use (interior access stairwell, removal of second kitchen, etc.) ~you 6 years ago. There are a lot of posts about single family to duplex but not the other way around. 

How risky would a purchase like this be? Assuming there is separate electrical meter and other standard duplex requirements, what are worst case or practical scenarios? Also, would it be difficult to get a loan based on the single family arrangement? Located in California. Thanks!