The size of the building and the zoning are irrelevant as to the type of property. If the use of the property is residential, then it is residential property. If the use of the property is office, retail, professional, industrial, etc. it is commercial property. Zoning only states how the property could be used. So a house, duplex or larger apartment building or condominium building were built on commercially zoned property which in urban areas is frequently the case, it is still a residential property. When it comes to financing, a loan on 5 or more residential units is considered a commercial loan by the bank, although the property is residential. The loan is a commercial type loan for a residential property. The use is what determines the type of property, not the zoning or the loan. In your case since the property consists of condominiums, each unit is a separate unit of ownership. There is not one loan on more than 5 units (a commercial type loan). There are 18 individual loans for 18 different owners of separately deeded property, and each loan is presumably a conventional residential loan.