What is the most likely source of leak?
Water leak on driver's side floor, cannot find source.Car has not had damage. on 2010 Toyota Corolla
Most likely cause is going to be a plugged evaporator drain for the air conditioner. If your car doesn't drip on the ground outside when the AC is running, then it's probably dripping inside the car on the passenger side floor. Also, check the coolant level. Although less likely because of the age of the car, you could also have a leaking heater core. If it is the plugged drain, that is an easy fix. Any shop should be able to do it for a nominal charge. The heater core can be a significant expense. However, being a 2010, your car may still be under warranty, depending on mileage.
Possible body seam improperly sealed.Does it only get wet when it rains? If so get a good (LED) flashlight to watch under dash (you might want to remove trim first for better view of upper corner)look from top down for dry water stains on backing of carpet/insulation .If nothing obvious , run a water hose on the outside of the windshield while watching inside AND listening for leak.Improvise and use common sense as to where best to direct water for the area you suspect the leak is from . also check for debris clogging drain tubes from windshield cowl(where the air enters for heat&a/c from outside).