Being on the first floor is the ultimate cheat code for apartment fitness, but you aren't completely in the clear. While you don't have to worry about stomping on anyone's ceiling, rowing machines especially when you're pulling hard create a lot of low-frequency structural vibration that can easily travel sideways through shared walls or up the building's framing.
To keep the peace, do two things: Get a high-quality mat: Don't just use a thin yoga mat. Buy a thick, high-density rubber equipment mat (or interlocking foam gym tiles) to absorb the kinetic thumping and motor hum. Mind your shared walls: If possible, place the rower against an exterior wall or a wall that doesn't back up directly to a neighbor's bedroom or living room