Prior to the sponsorhip approval, your parents need to be in Canada for at least one year so that you can request their PR application to be processed in U.S. Two requirements at that time:
1. Your parents need to be physically in Canada at the time of sponsorship is approved.
2. Your parents need to be continuously in Canada during the PR application processing period.
You are only preparing for the 1st stage documentation. Do not worry about things that won't happen in 3-4 years. Also about the application fees, Now you only need to submit it to Mississauga as it is the only CIC center for sponsorship approval.
1. Your parents need to be physically in Canada at the time of sponsorship is approved.
2. Your parents need to be continuously in Canada during the PR application processing period.
You are only preparing for the 1st stage documentation. Do not worry about things that won't happen in 3-4 years. Also about the application fees, Now you only need to submit it to Mississauga as it is the only CIC center for sponsorship approval.