For your consideration ...
Any thoughts on putting in a patio brick fireplace at a home in the CRE?
Does anyone have experiences in this? Any special regs? Distance from neighbor's line?
No special regs that I am aware of. Get yourself an old timer bricklayer to do the work. Just make sure it's gonna be built on a sufficiently high psi strength concrete slab. If you already have a concrete slab, setbacks, the distance from your neighbor's property line, has already been accounted for. Typically, most building setbacks are a minimum of 10 feet from property boundary lines, at least in Calvert. If you don't have a concrete slab already, depending on topography, you may need to grade the ground to install one, it's here you might need a grading permit.
Also, if you do have a concrete patio pad already, you really want to make sure it is sound and strong enough to bear the weight of that new brick fireplace, depending on the size you want of course. A good bricklayer should be able to determine if an existing concrete slab is thick enough, though maybe not in composition, to bear the fireplace's weight.
Or, if building to sit just off a patio, that a sufficient concrete footer is poured to a proper depth to support the weight proper.
A caveat: Do not attempt to build a brick fireplace on a wooden patio deck.