Buying Fourplex / Sixplex in Single Family Zoning Area

[Angel Meraz]

I'm interested in a fourplex building in the Fort Worth TX area but it's zoned as single family. The same owner is also selling the property next door which is a single family turned into a sixplex (basically a house turned into six units). As I was trying to get a hard money loan, the loan officer said the zoning would be an issue when trying to refinance due to the zoning. The seller would prefer to sell them together but also accepts offers separately.  

Does anyone know how big of an issue it would be to sort out the zoning and how likely it would be that the city would rezone either or both of them?