No, the rental property tax is not a business expense unless you are in the business of renting properties.
I know what you mean, but I can also see how others reading it can misunderstand it out of context because of your wording is all.
Property taxes paid on rental property are a deductible rental expense. There is a box in the rental expenses section specifically labeled "real estate taxes" and that's where you enter the property taxes paid. Note that if the property was converted to rental mid-year, then you may have to prorate the taxes and can only claim 1/12 of the taxes paid in the tax year, for each month the property was in service as a rental.
