Multi-Family Property vs. Accessory Dwelling Unit (ADU)

Making a determination between whether a property is a Multi-Family/Small Income property (duplex) or a single family dwelling with an Accessory Dwelling Unit (ADU) can be challenging in some circumstances. When the use is not readily apparent the appraiser has to make a determination. Some questions which assist in making the determination include:
 * How long has the current use been in effect? If longstanding, is the use grandfathered?
 * Is an ADU a legal use under current zoning?
 * Is a duplex property legal under current zoning?
 * Can the unit be rented under current zoning?
 * Do the units have separate electrical meters/utilities?
 * Do the units have separate addresses?
 * How has it been marketed in the past?
 * Is it now, or has it in the recent past, been rented to a non-family member to obtain rental income from it?
 * Is there a predominate use for similarly configured properties?