your query is not clear!!! you mean to say POF for 3 people? for 3 people bring arround CAD$18k is okay... POF enough to carry some amount in CASH + bank draft + travellers cheque.
why you pay for agent? POF you have to bring with you and show at POE in Canada when ask by officer @ airport, Agent or any bank will not help you (Latest Bank statement accepted if you have account with canadian bank, Indian or asian bank's statement not accepted like SBI OR Bank of baroda or any indian govt. banks).
POF should be in CAD $, USD , Euro or GBP accepted (INR not accepted please...), but must be enough POF for you + number of dependents , search more in this forum for POF.
OMM