Contact an area insurance provider for a ‘free’ quote (you would need to do this anyways when you complete your due diligence/financial analysis). They can usually turn the quote around in a day or so. Make sure you contact more than one provider as they may have different rates/specials.
What would you expect to pay annually for insurance on a $100,000 duplex? I know it depends on a number of factors but I am just looking for a ballpark figure. Any input would be greatly appreciated.