$600 is not true. You have to report all your income no matter how small. Even $1 of bank interest. If someone pays you they don't have to give you a 1099NEC unless it is 600 or more BUT you still have to report the income if it is less.
Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment. You pay 15.3% SE tax on 92.35% of your Net Profit (If it is greater than $400). The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare. So you get social security credit for it when you retire.
