It depends on what your goals are and how much time you are willing to commit. I try to convince all my clients to train at least 2 times a week to make sure there is adequate progress. If you are looking for a lot of results and a complete body transformation, I would recommend 4 to 5 times a week.
I specialize in training for athletic performance and injury prevention and rehabilitation.
My clients range from people that have never trained in their life to high level professional athletes.