Want an even better estimate? Call an insurance agent! (State Farm, American Family, Allstate, etc, etc.)
And no, I am not an insurance agent. (haha)
Best of luck with your multi-unit investment - a smart decision - you are on your way to a bright future!
Your credit score will also be a factor with some providers. Some weigh your score more or less for rates, some don't yet use your score. American Family is notorious for using your credit score to adjust rates. I've heard numerous horror stories from clients who's credit scores fell and American Family jacked their rates severely. One client had coverage for 12 years, never a claim, but his rates doubled+ when his credit score dropped during a divorce.