I paid my oldest daughter $100 per month to babysit her brother. Can I claim a $1200 babysitting expense and claim my daughter made a NET income of $1200?

If your oldest daughter is over the age of 18, you can claim these expenses & she will claim the income.

If your oldest daughter is under 18, she's not considered to be an eligible provider. Here's a link for more details: https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-re...