Commissioning a portrait is usually found to be an enjoyable process by all.
The sitting process involves getting together and my creating reference images, which may include sketches and usually photos (this is almost always the case with portraits of children).
Then one or two small composition studies will be done and sent to the client within a few weeks, giving the idea for the composition for the painting.
After approval of this sketch by the client, work begins on the final painting. This usually will be completed within three to six months of the initial sitting.
Payment is 1/3rd at the initial sitting, 1/3rd at the OK of the compositional sketch, and 1/3rd at completion of the portrait.
Your input into the process is welcome. I have never had a commission where those closest to the subjects of the painting did not have valuable suggestions about the portrait.
A portrait is a collaborative effort, with your happiness with the final work as our shared goal.