Right of permanent residence fee:
Principal applicant = CA$ 490
Spouse = CA$ 490
Children = CA$ 0 (do not have to pay)
http://www.cic.gc.ca/english/information/fees/fees.asp#rprf
http://www.cic.gc.ca/english/information/fees/fees.asp#rprf
You pay for "Right of permanent residence fee", when they ask for it. It is usually near the end of your application. If you get rejected before that they will not ask you for "Right of permanent residence fee".
So, just pay CA$ 550 per person when you apply. Don't worry about the "Right of permanent residence fee", they will send you a letter when they feel that your application will most likely be accepted.
www.cic.gc.ca/english/information/fees/fees.asp
www.cic.gc.ca/english/information/fees/fees.asp