Depends on the faucet. Most likely the sensor is in the faucet and all you will need is a receptacle under the sink. There are some that have a separate sensor that goes on the wall, but you could always fish that in later.
"Will it be cheaper if I drill the holes for you?"
Make sure you check the specs provided ! Most of the ones I have dealt with give an EXACT location for the electrical connection. Sinks are easier then toilets and urinals.Toilets and urinals have a location tolerance of about 0% they must be dead on.