Price depends on level of contamination, time involved,amount of product used. Until you inspect it I would not give a price. Also check for type of fiber, color crocking. Some rugs are better left to those who are equipped if its haitian cotton or similar the dyes can be very unstable. As for determining on site or off site that is your call not the customers if you are better equipped off site simply inform the customer of that. Make extensive inspection paperwork prior to removing or cleaning, don't let her headache become yours.