I give discounts if I feel like it (ie - repeat customers, friends). If somebody asks for one, forget it. When somebody keeps pressing and won't let up, "smart-ass Nick" makes a cameo: "Ok, I'll give you a discount. What part of the house would you like me to leave out of the inspection? Roof? Electrical? Heating?" I find this type of technique to be a very effective cheapskate repellant.