Before i enter my rental income i have a $9000+ refund. After i enter my rental income ($10,000 net) i have a refund of only $2000. Why am i getting taxed $7000 on $10,000 of income?
Without the details of your specific situation I can not explain in detail.
However, it is possible that the additional 10k of income pushed you into a higher tax bracket thus charging you more tax on your income/making lower income credits unavailable. Example going from 94k to 96k of income will cause an additional 6% tax.
Here is a quick reference link for the CRA tax brackets: