Note that parents are not classified as dependents for Canadian immigration purposes.
It will be at least four years before you can apply to sponsor your parents for PR. To qualify to sponsor them for PR, you must show that you have made enough money from a job in Canada to meet the income requirements for sponsorship for at least three years in a row. As part of the sponsorship process, you will need to submit three years of Canadian tax returns to prove you have made enough money to sponsor them.
Also, as of now, parent sponsorship is a lottery system where you have to apply and hope you are selected. So in addition to waiting until you have three years of tax returns, you will also have to wait until you are selected through the annual lottery which may take additional years.
