When guitarists with intermediate experience inquire about lessons, they usually have one of two objectives:  either to focus on a specific aspect of music theory or technique, or, a certain plateau has been reached and the guitarist isn't sure exactly what their next challenge should be.  To properly interview an advanced player, it usually takes thirty minutes to determine exactly what they know and wish to accomplish, and then to layout a gameplan for five or ten lessons.  With the consultation, there is no cost for the interview process, so by the first 'official' guitar lesson, a game plan is already developed and the learning process starts immediately.