You will need to create a separate TurboTax Online account. You can use the same e-mail address for up to five (5) different User Id's.
You may want to see if your son qualifies for the TurboTax Freedom Edition here: https://turbotax.intuit.com/taxfreedom/
For additional information please see the following TurboTax FAQ. https://ttlc.intuit.com/replies/3288574
