When I set a price, I always maintain that price. There are never any hidden fees, and I never collect payment until the job is completed to your satisfaction. At which point I will always do a walk through with the customer before accepting payment.
I will reach out to them to set up a time to meet in order to discuss what they are looking to get done. We then would meet, discuss their project as well as the cost of said project. Next, I would send an official estimate to the customer detailing all work that will be done and at what cost. Lastly, if the customer agrees to everything, we will discuss a good day and time for us to begin the work. No payment is ever requested prior to full post work completion.
I have been climbing recreationally on both rocks and in trees for my entire life. I feel just as comfortable in a tree as I do on the ground.