Driver side floor wet, mechanic says rack and pinon

If the floor is wet and he says the rack is bad then it would be oil. The rattle can be struts or even a shield hitting against the car when in motion. The wet floor might be a heater core leaking or the drain is plugged and not allowing condensation to drain. Put finger on it and rub together smell it if you can if it feels like coolant then have it checked for a heater core or drain plugged.