See: https://www.clergyfinancial.com/when-should-use-form-1099-nec/#:~:text=All%20businesses%20and%20orga....
But that's the church's concern. Your son does not need a 1099 to report the income.
The IRS considers undocumented cash income (no W-2 or 1099-NEC), for work performed, to be self employment income. You report the income from your own records. Enter at "Business Income & Expenses" and TurboTax (TT) will complete Schedule C for you and allow you to deduct any expenses associated with this income. You'll also have to pay self employment tax (social security & medicare tax) on any profits greater than $432.
You may have to upgrade to the Self Employment version of TT.
