Also, if you are only filing 2020 tax returns now, you will want to use the IRS free file version of Turbotax for your son. His income qualifies for free filing, but the standard turbotax "free to start" will up-charge to include the self-employment income.
https://freefile.intuit.com
Also note that for 2021, Turbotax is opting out of the IRS freefile program. Your most cost effective option at that point will be to purchase Turbotax as a CD or download to install on your own computer, since you can prepare all the returns for your family without paying extra. (State e-filing is extra, but your son won't have to file a state return if he only owes federal SE tax.)
