This is a very common question that I get from concerned parents so I thought I would weigh in with my electrical engineering background and over 10 years of experience in measuring the fields from high voltage powerlines as a professional EMF inspector.
First, you can never tell by looking what the electric or magnetic fields are from either the lines you see, or the ones you don't including a lot of newer suburbs which have underground lines or homes that have wiring errors in them. Just because you don't see a high voltage tower or other imposing electrical structure does not mean the property does not have a strong or intense pervasive fields.
Several other factors count with regard to the magnetic field generated by a feeder such as the number of conductors, phasing, amperage and physical geometry of the towers. The variance can be more than 2 orders of magnitude; for instance I have measured as little as 2 milliGauss (mG) below some very large 265 kV (kilovolt) lines and over 250 mG beneath others.
For relative comparison, the average home that does not have lines right next to the structure and has wiring within code is typically below 1 mG, but I have inspected some homes with serious wiring faults and measured 3 - 10 mG + even with no visible power lines in sight.
Also, how close is "close"?
For some prospective home buyers, even seeing the power lines a quarter mile away is disturbing while other people will purchase the home with the lines within arms length of the structure. My biggest concern with lines that are only a few feet away is as a fire hazard, not from the EMF. This is borne out by my personal experience in my home as I live in a heavily wooded neighborhood and twice a power line has come down in my yard and landed on the metal fence. The last time this happened, it actually caught the grass on fire, but fortunately I had just gotten home from work.
As for skeptics that do not believe in the health effects of EMF, I am not here to be a fearmonger or to convince anyone that they are wrong in their belief. There are a LOT of risk factors to consider with any home purchase from fire/flood hazard to nearby traffic density, air quality and crime.
For more answers to these and other questions, feel free to stop by my website at http://scantech7.com/EMF_Survey_FAQ.htm.
Good health to you and your families!
ScanTech EMF Inspections
"The Unusual Problem Specialist"