The market is huge. That is why this industry is growing so fast. You can not lose. But If you really want to make money, you have to market your website for all the services you offer. By the way, it will bring more visitors to your site and you can sell any other product.
Many people fail with any affiliate program because of one simple thing.
They DO NOT DO anything. They think that if they joined a program the money will come to them automatically. Sometimes it happens, of course, but not for everybody. You have to do something to make people to give you the money. You can put a text link or a banner to our site on your website.