I am in Frederick, MD. I know most counties in MD require new construction and major upgrades to include sprinkler systems. Like you stated, you want to verify with your own locality on the specifics.
I worked on a job in Charles County, MD a number of years ago and they did require it for every home we built (ground up). Unfortunately, that wasn't in the initial estimate, so the entire build out cost was wrong. And to top it off, it was 2008 so it's not like the sale prices were doing anything good to help matters. It hurt.
I'd definitely recommend what you're already doing and put in a call to your local jurisdiction to be 100%, but I'm guessing you'll need to put them in. See if you can get reduced insurance for that though- sometimes you can save a bit on the premium if it's a buy and hold.
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