[David Tan]

Also, even if you're thinking of doing it internally, it may be better to start with a network for a time before starting your internal program. Firstly, it's easier to manage an affiliate program through a network because the network will help you out with alot of the nitty gritty details. You can take time to learn as well as monitor how the program can grow with the influx of affiliates.
With a large number of affiliates, you can also test and fine-tune your commission structure and program settings to see what generates the most referral sales. The no hassle service of a network frees up time for you to do things you might not normally be able to do like to test marketing on different banner designs.

Lastly, time is money. Do you have the time, resources to do this? Is your business model suitable for affiliate marketing? What are some of the skills or knowledge that you are lacking? Questions, questions and more questions that will be answered faster with a network than the slow pace of an internal program. The faster you know all this, the better for you to make informed decisions and take quick actions.