if my only source of income is social security and my son pays me to watch his kid while he works do i need to file if we live in the same house dad watching not the mom

It depends on how much you received from babysitting our grandkid. If you received Social Security benefits plus other income, part of your social security might be taxable if your MAGI modified adjusted gross income(half of your Social Security, plus other sources of income) exceeds the base amount for your filing status ($32,000 for Married Filing Jointly or $25,000 for all others)

How Much Do You Have to Make to File Taxes?

So 16k I get in ss and he paid me 3k to baby sit so if that helps further answer my question 

Yes, you do need to file a tax return because the $3000 your son pays you to baby sit needs to be reported. The income needs to be reported as self-employed income. Here is how to report.

1. Open or continue your return.
2. Navigate to the self-employed income section:
   • TurboTax Online/Mobile: Go to self-employed income.
   • TurboTax Desktop: Search for self employed income (use this exact phrase, don't add a hyphen) and select the Jump to link.
3. Answer Yes on the Did you have any self-employment income or expenses? screen.
   • If you land on the Your 2024 self-employed work summary page, select Review next to the work you're adding income for.
4. Answer the questions on the following screens until you arrive at Let's enter the income for your work.
5. Select the form that applies to your situation and select Continue.