One of my first gigs was shots and video of the construction of a novel AM radio antenna design. I was very worried about near field radiation causing interference, but it really did not mess it up or interfere with my rc signal (as it shouldnt). Some thoughts on proceeding. Make sure to calibrate the compass, and even the imu onsite prior to flying. Make a note of any and all obstacles (guy wires, trees, the tower itself) make sure you know the altitude of the towers ceiling. Patience and planning will help you lots here.
Since you are functioning as the person getting visual data and not as an inspector (this would require proper certification) you should be pricing this accordingly. Make sure to factor in time for travel, fuel, insurance, and post processing into your fee. I would think since this is a danger close flight near critical infrastructure you wouldn't be unreasonable to expect $150 an hour (with flight time, planning, insurance, producibles considered) This will also depend on what producibles they want (photos, orthos, 3d models etc) Without knowing too much about the job i would think somewhere in the ball park of $300-$400 might work. Keep in mind this will vary with where you are and your competition, if someone else will do it for $250 you dont want to loose the business. Hope this helps!