We do have one lined up already.
It depends entirely on the area of the country you are in, the weather, and the excavator you have chosen. There is no average wait time. If you are building your own home, you are at a disadvantage with an excavator, and will be at a disadvantage with every subcontractor you deal with during the construction of your home. You are only building one home, while the builders they normally work for build multiple homes per year. Every subcontractor will put off your job and give priority to the builders who hire them month after month and year after year. Unfortunately, you may be a one shot deal. Good luck with your situation.