If you prepare tax returns for a fee and want to use Intuit software, consider ProSeries, Lacerte, or ProConnect Tax Online, as the license agreement for TurboTax prohibits its use for commercial purposes.
For more information, visit the Intuit Accountants website.
As a non-professional tax preparer, can I use these products?
You can, but it's probably overkill, not to mention expensive. Remember, you can use TurboTax to prepare as many returns as you want, as long as you don't charge for your services.