Building a (toy) Ghost Detector
There will be plenty of opportunity for detecting 60Hz around your house. You may however be disappointed with the distribution. There will be power and lighting wiring in almost any surface you look at. 

At a frequency of 60Hz, you won't see any EM radiation, it will all be electric or magnetic near field.

The way conventional wiring is done, with pairs of wires running in close proximity, this tends to minimise the wire separation and loop area, which minimises (intentionally) the near field electric and magnetic coupling to other things. In various places where the conductors don't run close together, say the wiring behind a socket, or the distribution panel, then you'll have a local 'hotspot' of increased coupling. You will find a strong electric field in very close proximity to a paired cable, which is how 'cable finders' work, but you need to be within an inch or so, none of this 'getting warmer' tension. Electric field hotspots will always be present. Magnetic field hotspots will come and go depending on where current is being drawn in the house.

You do have the opportunity to plant some enhanced transmitters of 60Hz, by plugging in things to sockets around the house. This might not work for the scenario, as they may well notice visually odd things plugged into the wall. Unfortunately there's nothing I can think of on the market that you can just buy that intentionally generates nice strong external 60Hz fields, so you may have to make stuff. This would depend on your being safe working with mains components.

A better solution might be to buy some ISM 'garage door opener' boards. You could sprinkle a few battery-powered transmitters around, and use the matching receivers in your ghost hunters.