How long will it take?
Solving a specific life problem could take a single session. Making some specific life change or getting relief from some specific symptom (like a phobia or panic disorder) could probably be accomplished in six to twelve sessions (2/3 of my clients in 2015 finished in 12 or fewer sessions).
In general, the deeper your problems and the higher your aspirations, the longer it takes and the harder it is to predict. I have been astonished at times when someone presenting really serious issues finished up in a few months, but that's rare. It doesn't usually take long to get back to where you were before the crisis; it takes longer to get to a new place in yourself and your life. Only a third of my clients in 2015 went beyond 12 sessions. Another quarter of them worked with me longer than six months before accomplishing their goals. Sometimes it takes years, especially if your early years were harsh or severely lacking in the support you needed to grow.