It is the best if you are good at promoting and selling product online. If you can't do any of those two that I mentioned, then affiliate marketing would not be for you.
As it relates to the network, it depends on which you prefer. There are there main affiliate location that I used but please note there are others network on the internet, which are just as effective.
These are the affiliate network that I use. Payspree, JVzoo and Clickbank. The first two mentioned pays you instant commission to your paypal account while clickbank pays you by check as soon as your total balance in account has reached $100