Credit inquiries have low impact on your credit score. Your credit score exists so you can use it to get the best rate. When shopping for something huge like a mortgage go crazy and shop around. Don't worry about an arbitrary number
Based on the simulator on MyFico.com, my score would drop by 5 points for an inquiry. That could be different in your case, and different versions of the FICO score could count it differently, but I would assume it to be in that ballpark.