There is no age limit to when to start treatment. Some problems cannot be corrected when there is no active growth and a few are best treated earlier.
Most orthodontic societies advise that an initial check-up screening appointment at 7 years of age takes place so that potential problems could be evaluated. Even if there are orthodontic problems at that age, most likely nothing will be done. During normal growth, the permanent teeth that erupt are generally larger than the space provided to accommodate them in a straight manner. Growth usually catches up and provides more space for your teeth to align on their own.
Your teeth and growth will be mostly monitored. In some cases and for specific problems only, intervention is necessary at this early stage.
Most treatments start between 10 and 13 when all the permanent teeth have erupted and there is growth that can be utilized in your favor.