Found a nice quiet, open spot for my maiden flight, but noticed that there are high-voltage power lines (the tower type) approximately 1/2 mile away. Will these cause any issues?
I'm just planning a simple beginner mode flight in the area directly around me with no intention of heading anywhere near the lines.

"Will these cause any issues?"

I doubt it. On multiple occasions I've flown much closer than that to the type of towers you described without any noticeable effect on the Mavic. I try to give power lines in general a wide berth, but that's more out of fear of colliding with them because they're hard to see through FPV until you're right upon them and because it's difficult to gauge the distance between them and the aircraft visually.

I've flown within a hundred feet with no problems.

I flew in front of and next to some highvoltage lines with no issues.

Until you fall and crash and kiss you MP goodbye... Stay away from power line, cell line, metal...

Have them over at my kids schools pump track and have had zero issues so far.