There won't be any regular income tax due on those low amounts but they will owe about 15% self employment tax on it.
They will have to fill out a Schedule C in their 1040 return. 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 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.
In case I wasn't clear they each need to file a tax return. You might consider using the Desktop CD/Download program. It can do unlimited returns and efile 5 for free. Buy the personal Desktop CD/Download programs here
https://turbotax.intuit.com/personal-taxes/cd-download/
