How safe/expensive is it to add some landscape lighting next to the walkway in front of my house?

Most landscape lighting systems use low-voltage lights. The normal household voltage of 110 volts is reduced to 12 volts by a transformer. This low voltage makes the lights extremely safe; you're unlikely to get a shock even if you touch bare wires or hit a buried cable while digging in the garden. (I don't recommend trying either of these, however!) Low-voltage systems are economical to operate. Most use less energy than a single 75-watt bulb. To save even more energy, you could put the lights on a timer that would automatically shut them off at a predetermined time each night. Or consider a solar-powered system, which harnesses sunlight during the day to power the lights at night.